Sclerosing adenosis of the prostate gland. A lesion showing myoepithelial differentiation

Sclerosing Adenosis of the Prostate-A Benign Lesion Similar to Prostate Cancer: A Case Report and Literature Review

Sclerosing adenosis of the prostate (SAP) is a rare benign non-neoplastic small acinar hyperplasia. Like sclerosing adenosis of the breast, which is confused with breast cancer, SAP is a trap in the pathological differential diagnosis of benign and malignant lesions of the prostate. We report such a case to help colleagues better distinguish and diagnose such diseases. A 75-year-old patient with SAP had a prostate specific antigen (PSA) level of 11.0 ng/mL, and he had been suffering from progressive dysuria for 3 years. The central glandular area and the right periphery of the prostate were found to have nodular low signals on magnetic resonance imaging (MRI). Prostate biopsy showed that basal cells were positive for P63 and P504s, few basal cells were positive for S-100, and the positive rate of Ki67 was approximately 2%. We consider that the possibility of SAP is high. The patient was treated conservatively and was discharged in good health, free of dysuria and other problems. SAP is a rare benign lesion that is easily misdiagnosed as prostate cancer. The prostatic gland tube has a complete basal cell layer surrounding it, as well as myoepithelial cell metaplasia of basal cells, which is a key trait in distinguishing it from prostate cancer. Although the latest research indicates that SAP does not require treatment, the question of whether it is a risk factor for prostate cancer remains unanswered.

Prostate sclerosing adenopathy: A clinicopathological and immunohistochemical study of twelve patients

BACKGROUND

Although sclerosing adenopathy of the prostate is a very rare benign disease, an effective differential diagnosis is required. Here, we report the clinicopathological and immunohistochemical morphological features of 12 cases of sclerosing adenopathy of the prostate to improve understanding of the disease.

AIM

To investigate the clinicopathological features, diagnosis, and immunohistochemical phenotypes that distinguish prostate sclerosing adenopathy from other conditions.

METHODS

The clinical data, laboratory tests, pathological morphology, and immunohistochemical phenotypes of 12 cases of prostatic sclerosing adenopathy were retrospectively analyzed, and the relevant literature was reviewed.

RESULTS

All patients were elderly men (mean age, 71.7 years; 62–83 years). Eleven of them had hematuria, urinary frequency, urinary urgency, difficulty in urination, and serum total prostate-specific antigen values within the normal range. One patient had increased blood pressure. Enlarged prostates with single to multiple calcifying foci were observed. Moreover, prostate tissue hyperplastic changes were observed in all patients. Small follicular hyperplastic nodules without an obvious envelope, with a growth pattern mimicking the infiltration pattern of "prostate adenocarcinoma" were noted. Basal cells expressed AR, CKH, P63, and CK5/6, and myoepithelial markers, such as calponin, S100, and smooth muscle actin. No recurrence or exacerbation of the lesions was observed, except for one case of death due to bladder cancer.

CONCLUSION

Prostatic sclerosing adenopathy is highly misdiagnosed as prostate adenocarcinoma or other tumor-like lesions. Therefore, it should attract the attention of clinicopathologic researchers.

Benign mimics of prostate cancer

The histopathological diagnosis of prostatic adenocarcinoma is challenged by the existence of numerous benign mimics. Most of these lesions have no clinical significance and many do not need to be reported. Their clinical relevance lies in the risk that they are misinterpreted as cancer. This review presents the histopathological features of benign mimics and discusses their distinction from cancer. The lesions that are most often misdiagnosed as cancer are atrophy and its variants, including simple atrophy, partial atrophy and post-atrophic hyperplasia. Benign proliferations are a group of lesions with crowded small glands with no or little nuclear atypia. The most problematic entity of this group is adenosis, which may have a more alarming architecture than some cancers. A diagnostic problem with atrophy and several of the benign proliferations is that the glands often have a discontinuous or absent basal cell layer. Hyperplastic and metaplastic lesions include basal cell hyperplasia. Basal cell hyperplasia may especially mimic prostate cancer with its small dark glands, variable nuclear atypia and a pseudoinfiltrative pattern, which may be present. The anatomical structure that most often causes diagnostic problems is the seminal vesicle. The mucosa of the seminal vesicle contains small acini, often with very pronounced nuclear atypia that may be misinterpreted as cancer. Pathologists need to be familiar with these mimics, as a false positive diagnosis of prostate cancer may lead to unnecessary radical treatment.

Benign mimics of prostatic adenocarcinoma

Benign mimics present either as common challenges in daily routine practice or may cause diagnostic dilemmas because some are less commonly seen and one may be less familiar in recognizing them. There are a multitude of mimics of prostatic adenocarcinoma, which may represent normal gland structures, benign proliferations, atrophic lesions, hyperplastic or metaplastic changes, and inflammatory processes. Some of them are preferentially found in certain anatomic areas of the prostate, either confined to the prostate, or outside of the gland. Various benign mimics of prostatic carcinoma may be also evaluated based on their morphologic similarity to Gleason patterns 3-5 of prostatic adenocarcinoma. Most of the mimics are easily recognizable in larger specimens, such as TUR of the prostate or radical prostatectomy specimens, but they may pose diagnostic problems when the evaluation is done on limited tissue, such as needle-core biopsies or if prostate specimens are infrequently encountered in practice. Therefore, before signing out a report with a diagnosis of prostatic carcinoma, pathologists should carefully consider and rule out the various benign lesions that may mimic carcinoma. This is particularly relevant in the current prostate biopsy practice which relies on using extended biopsy core templates. The awareness and familiarity with the characteristic features of the mimics and judicial use of additional ancillary tests, including immunohistochemistry can prevent overdiagnosis and false-positive interpretation. This review provides a contemporary update on the broad spectrum of the benign prostatic lesions that can mimic prostate adenocarcinoma, outlines their key morphologic and immunohistochemical diagnostic features, and provides a diagnostic, pattern-based approach in establishing a correct diagnosis and distinguishing them reliably from prostatic adenocarcinoma.

The benign mimickers of prostatic acinar adenocarcinoma

As the most frequent malignant histological subtype in prostatic cancer, prostatic acinar adenocarcinoma (PAA) has a series of benign mimickers including prostatic or non-prostatic lesions and normal structures, which may lead to an erroneous diagnosis and inappropriate treatment. It is very important to be aware of the existence of these mimickers and to recognize their histological features. The differential diagnosis should be based on a comprehensive evaluation of clinical history, histological structure, cytological morphology and the results of immunohistochemistry (IHC) staining, rather than on single criteria (e.g., the presence of prominent nucleoli or basal cell layer).

Updates in Benign Lesions of the Genitourinary Tract

The genitourinary tract is a common site for new cancer diagnosis, particularly for men. Therefore, cancer-containing specimens are very common in surgical pathology practice. However, many benign neoplasms and nonneoplastic, reactive, and inflammatory processes in the genitourinary tract may mimic or cause differential diagnostic challenges with malignancies. Emerging clinicopathologic, immunohistochemical, and molecular characteristics have shed light on the pathogenesis and differential diagnosis of these lesions. This review addresses differential diagnostic challenges related to benign genitourinary tract lesions in the kidney, urinary bladder, prostate, and testis, with emphasis on recent advances in knowledge and areas most common in diagnostic practice.

Nonneoplastic lesions of the prostate and bladder

CONTEXT

Specimens from the prostate and bladder are commonly encountered by the general surgical pathologist. Emphasis is usually placed on neoplasms of the bladder and prostate, particularly if malignant, owing to their therapeutic consequences. A good command of benign lesions occurring in the bladder and prostate, and knowledge of their preneoplastic potential will help pathologists confidently diagnose malignancy versus its benign mimickers and guide the urologists in choosing the appropriate therapy and follow-up for the patient.

OBJECTIVE

To present a mixture of benign entities, and discuss their histologic and clinical characteristics, hoping to provide a practical review for the general surgical pathologist.

DATA SOURCES

An extensive review of the literature on the entities discussed was performed.

CONCLUSIONS

A wide variety of benign entities are present in the prostate and bladder. Benign lesions in the prostate can be age related, such as prostatic atrophy and benign prostatic hyperplasia; transition zone associated, such as basal cell hyperplasia, adenosis, and sclerosing adenosis; or prostatic urethra associated. Benign lesions of the bladder encompass a wide variety of reactive changes that can occur in the urothelium, as well as hyperplastic lesions or reactive proliferations that could be misdiagnosed as malignant. The bladder responds to chronic irritation through several reactive/metaplastic lesions such as cystitis cystica/glandularis, keratinizing squamous metaplasia, or nephrogenic metaplasia. The urothelium can also give rise to hyperplastic/proliferative lesions, in particular von Brunn nest hyperplasia, papillary polypoid cystitis, and pseudocarcinomatous proliferation, which should be distinguished from malignant processes. Ectopic tissue, such as prostatic or mullerian, can also be seen.

The spectrum of morphology in non-neoplastic prostate including cancer mimics

The spectrum of morphology in non-neoplastic prostate includes lesions of prostatic epithelial origin, the most common being atrophy, including partial atrophy, adenosis (atypical adenomatous hyperplasia), basal cell hyperplasia and crowded benign glands, as well as those of non-prostatic origin, such as seminal vesicle epithelium. These lesions often mimic lower-grade prostatic adenocarcinoma whereas others, such as granulomatous prostatitis, for example, are in the differential diagnosis of adenocarcinoma, Gleason grades 4 or 5. Diagnostic awareness of the salient histomorphological and relevant immunohistochemical features of these prostatic pseudoneoplasms is critical to avoid rendering false positive diagnoses of malignancy.

Hybrid sclerosing adenosis and basal cell hyperplasia of the prostate

Hybrid sclerosing adenosis and basal cell hyperplasia of the prostate is a rare lesion. Here we report the seventh case of such lesions. Histological examination of the transurethral resection of the prostate of a 83-year-old Japanese man showed a small lesion consisted of sclerosing adenosis and basal cell hyperplasia, in addition to the diffuse glandular and fibromuscular hyperplasia. Immunohistochemically, many basal cells in sclerosing adenosis and basal cell hyperplasia areas showed a positive reaction for p63, cytokeratin 5, and D2-40. Additionally, many basal cells in the sclerosing adenosis area and some basal cells in the basal cell hyperplasia area were positive for S-100 protein and alpha-smooth muscle actin, which are myoepithelial cell markers. Finally, we suggest that hybrid sclerosing adenosis and basal cell hyperplasia may be actually a special form of hyperplastic lesion of all components of prostatic tissue, reflecting the unbalanced distribution of glandular, stromal (sclerosing adenosis), and basal cell hyperplasia with the differentiation toward myoepithelial cells predominantly occurring in a sclerosing adenosis area. Additionally, this case showed that D2-40 is a useful marker of basal cells.

Pseudoneoplastic mimics of prostate and bladder carcinomas

CONTEXT

The differential diagnoses of prostatic carcinoma and bladder epithelial neoplasms include several histologic mimics that should be known to avoid misdiagnosis.

OBJECTIVE

To discuss pseudoneoplastic lesions of the prostate and bladder that could potentially be confused with prostatic carcinoma and bladder epithelial neoplasms, respectively, with specific focus on their distinguishing histopathologic features.

DATA SOURCES

Relevant published literature and authors' experience.

CONCLUSIONS

Pseudoneoplastic lesions in the prostate include those of prostatic epithelial origin, the most common being atrophy, adenosis (atypical adenomatous hyperplasia), basal cell hyperplasia, and crowded benign glands, as well as those of nonprostatic origin, such as seminal vesicle epithelium. Such lesions often mimic lower-grade prostatic adenocarcinoma, whereas others, such as clear cell cribriform hyperplasia and granulomatous prostatitis, for example, are in the differential diagnosis of Gleason adenocarcinoma, Gleason grade 4 or 5. Pseudoneoplastic lesions of the urinary bladder include lesions that could potentially be confused with urothelial carcinoma in situ, such as reactive urothelial atypia, and others, such as polypoid/papillary cystitis, where papillary urothelial neoplasms are the main differential diagnostic concern. Several lesions can mimic invasive urothelial carcinoma, including pseudocarcinomatous hyperplasia, von Brunn nests, and nephrogenic adenoma. Diagnostic awareness of the salient histomorphologic and relevant immunohistochemical features of these prostatic and urinary bladder pseudoneoplasms is critical to avoid rendering false-positive diagnoses of malignancy.

Benign Mimickers of Prostate Adenocarcinoma on Needle Biopsy and Transurethral Resection

Prostate needle biopsy currently is the gold standard method for the diagnosis, management, and prognosis of prostate cancer. Obtaining an accurate diagnosis is crucial for pursuing proper patient management. This article discusses histologic mimickers of prostate carcinoma highlighting microscopic features that are helpful to reach a correct diagnosis and emphasizing potential diagnostic pitfalls.

Spindle cell lesions of the adult prostate

Prostatic spindle cell lesions are diagnostically challenging and encompass a broad array of benign and malignant processes. A subset of these lesions arises only within the prostate and generally represents entities that originate from the prostate epithelium or stroma, such as sclerosing adenosis, sarcomatoid carcinoma, stromal tumors of uncertain malignant potential (STUMP), and stromal sarcoma. Another subset of spindle cell tumors that involve the prostate are also found at other sites and include solitary fibrous tumor, leiomyosarcoma, and neural lesions among others. Finally, tumors may secondarily involve the prostate yet present as primary prostatic processes, as is evident with several cases of gastrointestinal stromal tumors (GIST). The utility of ancillary studies, including immunohistochemistry, is often limited and the main criteria for diagnosis are the morphologic findings by routine H&E stain. This review addresses the various entities that may present as spindle cell tumors within the adult prostate and discusses the functional aspects of the differential diagnosis of these lesions.

Benign mimickers of prostatic adenocarcinoma

The diagnosis of prostatic adenocarcinoma, especially when present in small amounts, is often challenging. Before making a diagnosis of carcinoma, it is prudent for the pathologist to consider the various benign patterns and processes that can simulate prostatic adenocarcinoma. A useful method of classifying benign mimickers is in relationship to the major growth patterns depicted in the classical Gleason diagram. The four major patterns are small gland, large gland, fused gland and solid. Most mimickers fit within the small gland category and the most common ones giving rise to false-positive cancer diagnosis are atrophy, post-atrophic hyperplasia, atypical adenomatous hyperplasia and seminal vesicle-type tissue. A number of other histoanatomic structures such as Cowper's gland, verumontanum mucosal glands, mesonephric glands and paraganglionic tissue may be confused with adenocarcinoma. Additionally, metaplastic and hyperplastic processes within the prostate may be confused with adenocarcinoma. Furthermore, inflammatory processes including granulomatous prostatitis, xanthogranulomatous prostatitis and malakoplakia may simulate high-grade adenocarcinoma. Atypical adenomatous hyperplasia (adenosis), a putative precursor of transition zone adenocarcinoma, has overlapping features with low-grade adenocarcinoma and may cause problems in differential diagnosis, especially in the needle biopsy setting. The pathologist's awareness of the vast array of benign mimickers is important in the systematic approach to the diagnosis of prostatic adenocarcinoma. Knowledge of these patterns on routine microscopy coupled with the prudent use of immunohistochemistry will lead to a correct diagnosis and avert a false-positive cancer interpretation.

Mesonephric remnants of the prostate: incidence and histologic spectrum

Mesonephric remnants in the prostate are an unusual mimic of adenocarcinoma with unknown incidence. This condition is considered benign, similar to its counterpart in the female genital tract, but there have only been six cases reported to date, so the histologic spectrum of this finding is uncertain. To determine the incidence and comparative histopathology of this finding, we reviewed all transurethral resections of the prostate obtained at Mayo Clinic (Rochester, MN) in 1989 to identify cases of mesonephric remnants. Among 698 prostatic transurethral resection specimens, we identified 4 cases of mesonephric remnants (0.6% incidence), all in association with nodular hyperplasia. Patients ranged in age from 66 to 82 years (mean, 72 y) and had typical urinary obstructive symptoms; follow-up was obtained in these 4 cases. Four additional consultation cases and one needle biopsy case were also included in this study. Histologically, mesonephric remnants consisted of a proliferation of benign acini arranged in lobules or showing infiltrative growth between smooth muscle bundles without stromal desmoplasia. The acini were typically round or oval, varied in size and spacing, and lined by a single layer of low cuboidal cells with scant to moderate cytoplasm and inconspicuous small nucleoli. The cells of mesonephric remnants were not reactive with antibodies to prostate-specific antigen (eight of eight cases) or with prostatic acid phosphatase (seven of seven cases); high-molecular weight cytokeratin 34betaE12 was positive in the basal cells (six of eight cases). Our results indicate that mesonephric remnants are present in <1% of transurethral resections and are rarely identified in needle biopsies. The acini are lobular or infiltrative and may be architecturally mistaken for adenocarcinoma. This cytologically innocuous finding is probably underreported and interpreted as benign prostatic acini, but this is of no apparent clinical consequence. Immunohistochemical studies with antibodies to PSA and keratin 34BE12 are helpful in separating mesonephric remnants from adenocarcinoma, similar to the case of other benign mimics.

Sclerosing adenosis of the prostate. Histologic features in needle biopsy specimens

Sclerosing adenosis of the prostate is a pseudoneoplastic lesion that can mimic prostate cancer. Because the lesion is more common in the transition zone, which is only rarely sampled in needle biopsy, it is uncommon to see examples of this lesion in biopsy specimens. Because sampling of the transition zone of the prostate is likely to become more frequent, practicing surgical pathologists must be aware of the morphologic features of sclerosing adenosis of the prostate in needle biopsy specimens, in order to avoid misinterpretation of sclerosing adenosis of the prostate, a benign lesion, as prostate adenocarcinoma. We report the morphologic findings of sclerosing adenosis of the prostate in 3 needle biopsy specimens from 2 patients diagnosed as having sclerosing adenosis. We found a combination of histologic (mainly a cellular myxoid stroma and a double-cell population of acinar cells) and immunohistochemical features demonstrating a continuous basal cell layer with myoepithelial differentiation to be diagnostic.

Morphologic criteria for the diagnosis of prostatic adenocarcinoma in needle biopsy specimens. A study of 250 consecutive cases in a routine surgical pathology practice

CONTEXT

The diagnosis of prostate adenocarcinoma in needle core biopsy specimens is based on multiple diagnostic criteria and supportive features, most of which have been defined mainly from observations in transurethral resection and prostatectomy specimens. There is little information on the frequency with which diagnostic and supportive features of prostate cancer occur within benign glands. The few reports dealing with diagnostic criteria of cancer in needle biopsies have been largely confined to analysis of selected cases that posed particular diagnostic difficulty.

OBJECTIVE

To analyze the frequency with which numerous diagnostic or supportive features of prostate cancer occur in an unselected, consecutively performed series of 18-gauge prostate needle biopsy specimens.

DESIGN

Two hundred fifty consecutive 18-gauge prostate needle biopsy specimens (150 malignant and 100 benign) were evaluated, using hematoxylin-eosin-stained histologic sections.

RESULTS

The frequency of the histologic features in malignant and benign glands was as follows: prominent nucleoli (94% and 25% of malignant and benign specimens, respectively), marginated nucleoli (88% and 7%), multiple nucleoli (64% and 0%), blue-tinged mucinous secretions (52% and 0%), intraluminal crystalloids (40.6% and 1%), intraluminal amorphous eosinophilic material (86.7% and 2%), collagenous micronodules (2% and 0%), glomerulations (15.3% and 0%), perineural invasion (22% and 0%), retraction clefting (38.6% and 7%), and invasion of fat (0.7% and 0%).

CONCLUSIONS

Since not all diagnostic or supportive features of cancer are evident in any single case of cancer, particularly in needle biopsy specimens in which sampling is limited, awareness of these data would be helpful in the assessment of small foci of atypical glands being considered for cancer.

The distribution of S-100 protein in hyperplastic and neoplastic prostatic epithelium

Specimens from 30 cases of benign prostatic hyperplasia and 75 cases of prostatic carcinoma obtained during suprapubic prostatectomy, transurethal resection of the prostate and radical prostatectomy, were stained immunohistochemically for S-100 protein, prostatic acid phosphatase (PAP), prostatic specific antigen (PSA), neuron specific enolase (NSE) and polyclonal keratin. S-100 protein was positive in 9.3% of prostatic carcinomas and negative in all cases of prostatic hyperplasia. PAP and PSA were positive in all cases, while NSE was positive in 16% of the carcinoma cases. Polyclonal keratin was positive in both cell layers of the double layered hyperplastic prostatic epithelium with a more intense staining pattern in the outer cell layer. The authors believe that the S-100 protein immunoreactivity observed in some prostatic carcinomas, reflecting the change in the functional status of the neoplastic cells, might be of prognostic significance. They also emphasize the non-myoepithelial nature of the outer cell layer of the double layered prostatic epithelium.

Prostate Cancer - Old Problems and New Approaches. (Part II. Diagnostic and Prognostic Markers, Pathology and Biological Aspects)

Diagnostic and prognostic markers for prostatic cancer (PCa) include conventional protein markers (e.g., PAP, PSA, PSMA, PIP, OA-519, Ki-67, PCNA, TF, collagenase, and TIMP 1), angiogenesis indicator (e.g., factor VIII), neuroendocrine differentiation status, adhesion molecules (E-cadherin, integrin), bone matrix degrading products (e.g., ICPT), as well as molecular markers (e.g., PSA, PSMA, p53, 12-LOX, and MSI). Currently, only PSA is used clinically for early diagnosis and monitoring of PCa. The histological differential diagnosis of prostatic adenocarcinoma includes normal tissues such as Cowper's gland, paraganglion tissue and seminal vesicle or ejaculatory duct as well as pathological conditions such as atypical adenomatous hyperplasia, atrophy, basal cell hyperplasia and sclerosing adenosis. A common PCa is characterized by a remarkable heterogeneity in terms of its differentiation, microscopic growth patterns and biological aggressiveness. Most PCa are multifocal with signi ficant variations in tumor grade between anatomically separated tumor foci. The Gleason grading system which recognizes five major grades defined by patterns of neoplastic growth has gained almost uniform acceptance. In predicting the biologic behavior of PCa clinical and pathological stages are used as the major prognostic indicators. Among the cell proliferation and death regulators androgens are critical survival factors for normal prostate epithelial cells as well as for the androgen-dependent human prostatic cancer cells. The androgen ablation has been shown to increase the apoptotic index in prostatic cancer patients and castration also promotes apoptotic death of human prostate carcinoma grown in mice. The progression of PCa, similarly to other malignancies, is a multistep process, accompanied by genetic and epigenetic changes, involving phenomenons as adhesion, invasion and angiogenesis (without prostate specific features).

Minimal criteria for the diagnosis of prostate cancer on needle biopsy

Increased clinical screening of men at risk for prostate cancer, and the realization of the benefits of performing multiple biopsies per prostate, have facilitated early detection of malignancy, while presenting the pathologist with a growing array of diagnostic findings. Interpretation of these findings requires discussion of the minimal criteria required for the diagnosis of cancer on needle biopsy within a wide spectrum of related histologic findings. This spectrum includes small acinar proliferations suspicious for but not diagnostic of cancer, benign mimics of cancer, the preinvasive entity of high-grade prostatic intraepithelial neoplasia, and various treatment effects. Clinical implications of these findings and other prognostic factors are detailed.

Prospective origins of prostate carcinoma. Prostatic intraepithelial neoplasia and atypical adenomatous hyperplasia

BACKGROUND

The search for the precursor of prostatic adenocarcinoma has focused in recent years on two histopathologic findings: high grade prostatic intraepithelial neoplasia (PIN) and atypical adenomatous hyperplasia (AAH). This article describes the diagnostic criteria and clinical significance of PIN and AAH.

METHODS AND RESULTS

PIN is the most likely precursor of prostate carcinoma. The continuum that culminates in high grade PIN and early invasive carcinoma is characterized by progressive basal cell layer disruption, loss of markers of secretory differentiation, nuclear and nucleolar abnormalities, increasing proliferative potential, increasing microvessel density, variation in DNA content, and allelic loss. Clinical studies suggest that PIN predates carcinoma by 10 years or more, with low grade PIN first appearing in men in their 30s. AAH is usually found in the transition zone, and shows a weak and inconclusive link to well differentiated adenocarcinoma of the transition zone.

CONCLUSIONS

The significance of recognizing PIN is based on its strong association with prostatic carcinoma. PIN coexists with carcinoma in most cases, but retains an intact or fragmented basal cell layer, unlike carcinoma, which lacks a basal cell layer. High grade PIN in biopsies predicts the presence of carcinoma in subsequent biopsies, and PIN provides the highest risk ratio of all known predictive factors. This finding indicates the need for repeat biopsy and follow-up when PIN is identified in a biopsy, especially in patients with an elevated serum prostate specific antigen concentration. PIN also offers promise as an intermediate endpoint in studies of chemoprevention of prostatic carcinoma. Unlike PIN, AAH is weakly linked to carcinoma, and current data indicate that no follow-up is necessary for patients with this finding.

Pre-neoplastic lesions of the prostate

Acinar carcinoma of the prostate is the third most frequently registered cancer and its incidence is expected to increase as life expectancy increases. Consequently, there have been attempts to introduce possible screening programmes for early detection of prostatic carcinoma. In this context the histopathologist has a role in that potential pre-neoplastic lesions have to be recognized. Two such pre-neoplastic lesions in the prostate are adenomatous hyperplasia and prostatic intraepithelial neoplasia. In this article the histological features of these lesions, their differential diagnosis and their pre-malignant potential are reviewed.

The extent and zonal location of prostatic intraepithelial neoplasia and atypical adenomatous hyperplasia: relationship with carcinoma in radical prostatectomy specimens

High grade prostatic intraepithelial neoplasia (PIN) and atypical adenomatous hyperplasia (AAH) are considered putative precursors of prostatic adenocarcinoma. We determined the extent and zonal distribution of PIN and AAH in totally-embedded radical prostatectomies with prostate cancer, including 195 cases with PIN and 217 with AAH. PIN was identified in 86% of the cases. The mean volume of PIN was 1.32 cc (range, 0-8.12 cc), and was greater for PIN within 2 mm of cancer (mean, 1.0 cc) than for PIN more than 2 mm from cancer (mean, 0.3 cc). PIN was usually multicentric (64.5% of cases) and located in the non-transition zone (63%) or all zones (36%). The volume of PIN was positively correlated with the volume of cancer, patient age, pathologic stage and Gleason score. AAH was identified in 23.0% of the cases, and was more frequent in the transition zone (19.8% of cases) than in the non-transition (peripheral and central) zone (6.0%). The number of foci of AAH in the transition zone was always greater than that in the non-transition zone. AAH was frequently multicentric (46% of cases), especially in the transition zone (47% of transition zone cases) compared with the non-transition zone (23% of non-transition zone cases). The mean volume of AAH was 0.029 cc (range, 0-1.29 cc), and was much higher in the transition zone than in the non-transition zone. AAH was more common in older patients and those with greater prostatic weight, higher prostatic volume, greater percent of nodular hyperplasia, greater volume of cancer, greater percent of Gleason patterns 4 and 5 cancer, higher volume of prostatic intraepithelial neoplasia and higher serum prostate specific antigen concentration. Our results indicate that the extent and zonal distribution of high grade PIN and carcinoma are strongly associated, and that PIN is frequently multicentric; this supports the hypothesis that PIN is a premalignant lesion. AAH and carcinoma show a weak but significant association; if AAH is a premalignant lesion, it probably is associated with a subset of cancers arising in the transition zone.

Mucin expression in atypical adenomatous hyperplasia of the prostate

Prostatic atypical adenomatous hyperplasia (AAH) is a small glandular proliferation that has histological similarities with well-differentiated adenocarcinoma. To determine the histochemical profile of AAH, we assessed the production of total neutral mucin, total acidic mucin, and sulfated acidic mucin in 24 cases of AAH, five cases of Gleason primary pattern 1 and 2 adenocarcinoma, and 29 cases of adjacent benign and hyperplastic prostatic tissue. All specimens were formalin-fixed transurethral resections, and the diagnosis in each was confirmed by evaluation of the keratin 34B-E12 immunoreactive basal cell layer (intact in benign and hyperplastic epithelium, fragmented in AAH, and absent in cancer). The extent of mucin staining was measured semiquantitatively in 10% increments according to the number of stained glands. Neutral mucin was found in all but two cases, and there was no apparent difference in the amount of staining in benign glands, AAH, and cancer (mean number of stained glands, 43%). Total acidic mucin was more common in AAH (63% of cases; mean, 11% of glands) and adenocarcinoma (60% of cases; mean, 30% of glands) than in benign glands (0% of cases). Similarly, nonsulfated acidic mucin was more common in AAH (63% of cases; mean, 12% glands) and adenocarcinoma (60% of cases; mean, 8% of glands) than in benign glands (0% of cases); the pattern and intensity of staining for nonsulfated acidic mucin appeared to be similar to that for total acidic mucin in AAH and cancer. These findings indicate that there is a close relationship in mucin expression between AAH and well-differentiated adenocarcinoma. Identification of acidic mucin should be used cautiously as an adjunct in the diagnosis of adenocarcinoma but is useful in separating some cases of AAH and adenocarcinoma from benign prostatic epithelium.

Utilization of high molecular weight cytokeratin on prostate needle biopsies in an independent laboratory

OBJECTIVES

Immunoperoxidase staining of prostate tissues with antibodies to high molecular weight cytokeratin, which selectively labels basal cells, has recently been shown to be useful in the diagnosis of prostate cancer in academic centers. A growing sector in pathology is large independent laboratories, where little is known regarding practice patterns. The following study evaluated the use of high molecular weight cytokeratin in an independent laboratory specializing in prostate needle biopsies.

METHODS

In a 2-month period (July 1, 1994 to August 31, 1994), 4047 prostate needle biopsies were evaluated.

RESULTS

Without the use of ancillary studies, 2710 (67%) were diagnosed as benign, 978 (24.1%) were diagnosed as cancer, and 23 (0.6%) were diagnosed as high-grade prostate intraepithelial neoplasia. The remaining 336 atypical cases (8.3%) were further evaluated with antibodies to higher molecular weight keratin. Of the 336 cases, 253 (6.2% of total) were resolved as diagnostic for cancer, 68 (1.7% of total) were diagnosed as benign, and 15 (0.4% of total) remained atypical. The cost of performing high molecular weight cytokeratin was approximately $5.00 per case, which was not passed on to the patient.

CONCLUSIONS

The use of high molecular weight cytokeratin decreased the rate of an atypical prostate biopsy from 8.3% to 0.4% at a negligible cost to the pathologist and patient.

Florid basal cell hyperplasia of the prostate

Florid basal cell hyperplasia of the prostate is an uncommon proliferative condition, most often associated with adenomatous hyperplasia. It is considered a benign lesion although confusion with prostatic cancer is possible when one is not familiar with the histopathological appearance. We report another two cases of the glandular type of basal cell hyperplasia with immunohistochemical findings. Both lesions were composed of crowded and rather small glands with piling up of basaloid cells. They showed immunohistochemical positivity for high molecular weight cytokeratin 34 beta E12, confirming their relationship with basal cells. We detected focal positivity of these basal cells for alpha-smooth muscle actin, suggesting myoepithelial differentiation. Paucity of actin-positive smooth muscle cells in the stroma was noticed. One of the lesions showed some mild cytological atypia with prominent nucleoli and increased mitotic activity.

Benign and malignant neoplasms of myoepithelial cells: cytologic findings

We report two myoepithelial cell neoplasms; a salivary gland tumor was malignant and a breast neoplasm was benign. Both were studied histologically, immunohistochemically, cytologically, and ultrastructurally. The malignant myoepithelioma recurred twice and metastasized to one regional lymph node. This tumor was infiltrative with areas of necrosis and hemorrhage. It was composed of malignant-appearing spindle and plasmacytoid cells. Both types of cells were immunoreactive to muscle specific actin, S-100 protein, cytokeratin, vimentin, and neuron-specific enolase. Ultrastructurally, features of myoepithelial cells were seen. Fine-needle aspirate smears showed spindle and plasmacytoid cells, numerous mitoses, and malignant-appearing nuclei. Spindle-cell adenomyoepithelioma of the breast, a small well-circumscribed firm nodule, featured multiple lobules of spindle cells associated with clear-cell glands at the lobular periphery. Histologically and cytologically, the lesion was cellular but appeared benign. The differential diagnosis of myoepithelial neoplasms is discussed.

Atypical adenomatous hyperplasia of the prostate: morphologic criteria for its distinction from well-differentiated carcinoma

Atypical adenomatous hyperplasia (AAH) is a localized proliferation of small glands within the prostate that may be mistaken for carcinoma. To determine the diagnostic criteria for separating AAH from carcinoma, seven observers independently evaluated 54 selected lesions from 44 transurethral resection specimens. Three patterns of glandular proliferation were observed, all arising in association with nodular hyperplasia: AAH (38 foci), atypical small acinar proliferation of uncertain significance (eight foci), and well-differentiated carcinoma (eight foci). Of 24 architectural and cytologic features evaluated, the following were useful in separating these three patterns: variation in nuclear size (14%, 22%, and 25%, respectively), mean nucleolar diameter (0.69 micron, 1.43 microns, and 1.78 microns, respectively), largest nucleolar diameter (mean, 1.66 microns, 2.71 microns, and 2.81 microns, respectively), percentage of nucleoli greater than 1 micron in diameter (17.6%, 58.1%, and 77.5%, respectively), crystalloids within suspicious glands (16%, 13%, and 75%, respectively), luminal basophilic mucinous secretions, infiltrative borders, discontinuity of the basal cell layer in AAH (compared with complete absence in carcinoma; shown with basal cell-specific anti-keratin monoclonal antibody 34 beta E12 immunostaining), and intact basement membrane in AAH (compared with discontinuity in carcinoma; shown with type IV collagen immunostaining). Features that could not reliably separate AAH from carcinoma included lesion shape, circumscription, multifocality, average gland size, variation in gland size and shape, nuclear shape, chromatin pattern, and amount and tinctorial quality of cytoplasm. Although the biologic significance of AAH is uncertain, its light microscopic appearance and immunophenotype allow it to be distinguished from carcinoma in most cases.