Fine-needle aspiration features of pilomatrixoma

Fine-needle Aspiration Biopsy of Pilomatrixoma (Cytological Features of Six Cases Histologically Approved)

Background and Objective

Pilomatrixoma is a rare, benign, slow-growing tumor of the hair matrix. Excisional biopsy is often the preferred method of diagnosis for cutaneous masses including pilomatrixoma. However, fine-needle aspiration is also performed on these lesions. There are very few reports on the cytologic features of pilomatrixoma in fine-needle aspiration. In this study, we aimed to evaluate the clinical and cytological features of six cases of pilomatrixoma, which were confirmed histopathologically.

Materials and Methods

The study includes six cases of pilomatrixoma, which were diagnosed by two cytopathologists in 2019 and 2022. A detailed cytological analysis was done by a semiquantitative method. Cellularity, basaloid cells, squamous cells, giant cells, shadow cells, naked nuclei, calcium deposits, inflammation, and debris were semiquantified from 0 to 3+.

Results

The ages of patients ranged from 8 to 63 years old. The male-to-female ratio was 2:1. All cases occurred in the head and neck area. The cytological diagnosis was pilomatrixoma in five cases and epidermoid/dermoid cyst in one case. The surgical excision was performed in all patients. The diagnosis of pilomatrixoma was confirmed histologically in all cases.

Conclusıon

Fine-needle aspiration biopsy (FNAB) of pilomatrixoma can be a diagnostic challenge. There are very few reports on the cytologic features of pilomatrixoma in FNAB smears. The presence of ghost cells and basaloid cells should suggest the possibility of pilomatrixoma. The presence of giant cells, fibrillary matrix, calcium deposits, squamous cells, naked nuclei, inflammation, and debris are cytological findings supporting the diagnosis.

Integrating vascularity into the pattern classification of pilomatricomas on ultrasound provides a more competent approach for discriminative evaluation

BACKGROUND

Pilomatricoma has various manifestations on color Doppler ultrasound, and a differential diagnosis is challenging. The objective of this study was to investigate which characteristics of skin lesions on color Doppler ultrasound are effective in distinguishing pilomatricoma from epidermoid cyst and dermatofibrosarcoma protuberans.

MATERIALS AND METHODS

Records of patients with pilomatricomas (n = 63), epidermoid cysts (n = 76), and dermatofibrosarcoma protuberans (n = 19) who underwent color Doppler ultrasound evaluation and surgical excision were reviewed. The anatomical distribution and color Doppler ultrasound characteristics of these lesions were analyzed. The 63 pilomatricomas were categorized into five types based on their color Doppler ultrasound characteristics, and the roles of these five types in the differential diagnosis of the aforementioned diseases were studied.

RESULTS

Pilomatricomas, epidermoid cysts, and dermatofibrosarcoma protuberans exhibited some similar characteristics. Dominantly markedly hyperechoic or hyperechoic appearance, posterior acoustic shadowing, and the presence of vascularity were the major characteristics of pilomatricomas. The pilomatricomas could be categorized into five types, with type II having a diagnostic performance of sensitivity of 65.08%, specificity of 98.95%, area under the receiver operating characteristic curve (AUC) of 0.743, positive predictive value of 97.62%, and negative predictive value of 81.03% for the diagnosis of the aforementioned skin diseases.

CONCLUSION

A combination of dominantly markedly hyperechoic or hyperechoic appearance, posterior acoustic shadowing, and the presence of vascularity exhibits higher diagnostic performance for the differential diagnosis of pilomatricomas, epidermoid cysts, and dermatofibrosarcoma protuberans.

Pitfalls in Lymph Node Fine Needle Aspiration Cytology

BACKGROUND

Fine needle aspiration cytology (FNAC) is an accurate, minimally invasive, and cost-effective biopsy method for enlarged lymph nodes. While the role of lymph node FNAC in the diagnosis of infectious or reactive conditions and metastatic malignancy is unquestioned, differing views still exist on its role in the diagnosis of lymphoma. Nevertheless, regardless of the practice setting, pitfalls and potential for error exist, and it is incumbent upon the pathologist to be aware of these pitfalls, as this is the first line of defence against errors.

SUMMARY

This discussion will focus on potential interpretational errors, specifically highlighting scenarios leading to false-negative and false-positive diagnosis and errors in tumour classification, with an emphasis on cytomorphology. Potential entities that may fly below the radar of the pathologist - so-called off-radar entities - are also discussed, as a reminder to consider broad differentials in cases with unusual morphologic features. Some reasons for false-negative diagnoses include low-grade lymphomas that mimic a mixed, polymorphous reactive lymphoid population or aspirates with a paucity of lesional cells, through either sampling error or the intrinsic nature of the entity, e.g., nodular lymphocyte predominant Hodgkin lymphoma. Some of the potential causes of false-positive diagnoses that are discussed include viral-associated lymphadenopathy, Kikuchi-Fujimoto lymphadenitis, or benign adnexal lesions mimicking metastatic malignancy. Errors in tumour classification covered include metastatic carcinoma, sarcoma, melanoma, and lymphoma mimicking each other, and Hodgkin lymphoma and its mimics. Finally, less common entities such as follicular dendritic cell sarcoma and others are briefly mentioned, to remind us of conditions that may slip under our diagnostic radar.

KEY MESSAGES

A systematic review of diagnostic pitfalls and traps is elucidated here, with some tips to avoid these traps. The triple approach to the diagnostic workup is emphasised, which includes rigorous clinicopathologic correlation, attention to cytomorphology, and judicious application of ancillary tests.

Pilomatrixoma of the Arm: A Case Report and Review of Literature

Pilomatrixoma (PMX), also known as calcifying epithelioma of Malherbe, is a rare benign neoplasm that arises from the hair matrix cells, commonly in the head, neck, and upper trunk regions, infrequently affecting upper and lower extremities. It has to two peaks of presentation: under 20 years of age or between 50 and 65 years of age, slightly more common in females. The neoplasm exhibits diverse clinical manifestations and is frequently subject to misdiagnosis with alternative dermatological diseases. We present an atypical case of PMX affecting the upper extremity of a 62-year-old female patient. Surgical removal of the affected tissue under local anesthesia was performed, and subsequent histopathological analysis confirmed the presence of PMX. Based on the literature search we performed, we found out that this pathology is underreported in Jordan, with only one study published describing this tumor in the maxillofacial region. Physicians should be aware of this condition and its different presentations to include it in the differential diagnosis of suspected cases to provide the appropriate management and follow-up.

Cytological Diagnosis of Pilomatrixoma and its Diagnostic Pitfalls

Background

Pilomatrixoma (PMX) is a relatively uncommon benign cutaneous neoplasm arising from skin adnexa. It presents as a subcutaneous asymptomatic nodule mostly in the head and neck region and is frequently misdiagnosed by the clinicians. Although easily diagnosed on histopathology, the cytologic features of PMX are less distinctive, depending on the stage and evolution of disease and may mimic other benign or even malignant lesions.

Aim

To study the cyto-morphological features of this uncommon neoplasm and identify its potential diagnostic pitfalls on fine needle aspiration cytology (FNAC).

Material and Methods

Archival records of histopathologically diagnosed Pilomatrixoma were analyzed during study period of 2.5 years. Clinical diagnosis, preoperative FNA characteristics, and histopathological details were studied in each case. Cytologic pitfalls resulting in misdiagnosis of PMX cases on FNAC were evaluated in discordant cases.

Results

The series showed male preponderance, with head and neck being the commonest site. Out of 21 histopathologically proven cases of PMX, cytological correlation was available in 18 cases. A correct cytologic diagnosis of PMX/adnexal tumor was rendered in 13 cases. Erroneous diagnosis was given in 5 cases mainly because of the predominance of one component over the other or non-representative-aspirated material.

Conclusion

The present study highlights the importance of careful screening of FNAC smears keeping in mind the variability in the relevant cytologic features of PMX and creates awareness about the lesions that can mimic Pilomatrixoma resulting in diagnostic dilemma.

A Case Report of a Rapidly Growing Giant Pilomatrixoma on the Posterior Shoulder in a 12-Year-Old Male Patient

Introduction

Giant pilomatrixomas are quite rare and can be clinically challenging to diagnose.

Case Presentation

Here, we report a case of a rapidly growing mass on the shoulder of a 12-year-old previously healthy boy. The lesion on his right shoulder appeared as a painless, pink-blue-colored solitary mass that started 6 months ago and rapidly enlarged to 4.5 × 6 cm in size. Previous biopsy results were inconclusive, showing only hypercellular spindle cell proliferation in a collagenous stroma. There was concern for malignancy versus mixed lymphatic venous malformation or benign soft tissue tumor. An excisional biopsy was done and demonstrated features of a pilomatrixoma. Complete surgical removal with clear margins was curative.

Conclusion

Diagnosis and management of rapidly enlarging skin lesions in children can be difficult for clinicians and dermatopathologists. Excisional biopsy can be both diagnostic and therapeutic. A timely exclusion of malignancy is of utmost importance.

Novel Mutations in Pilomatrixoma, CTNNB1 p.s45F, and FGFR2 p.s252L: A Report of Three Cases Diagnosed by Fine-Needle Aspiration Biopsy, with Review of the Literature

Pilomatrixoma (calcifying epithelioma of Malherbe) is an uncommon benign skin appendageal tumor that differentiates toward hair matrix cells. It is misdiagnosed in up to 75% of cases by nondermatologists. Although the histopathological findings are well recognized and characteristic, diagnosis by fine-needle aspiration biopsy may be quite challenging. Several reports have emphasized the challenges in cytodiagnosis of pilomatrixoma, leading to a false-positive diagnosis. The lesions may show avidity for fludeoxyglucose on positron emission tomography/computed tomography scan, raising concern of a possible malignant neoplasm. CTNNB1 mutations have been reported in a high percentage of pilomatrixomas. Expression of β-catenin, the protein encoded by CTNNB1, is also frequently observed. To determine if routine cytological specimens can be successfully used to perform additional investigation and support or confirm the diagnosis in three cases of pilomatrixoma, we performed molecular analysis and immunohistochemistry to search for CTNNB1 mutation and β-catenin, respectively. β-Catenin positivity by immunohistochemistry was observed in basaloid cells in all three cases. Exon 3 mutations in CTNNB1 were detected in all cases. In addition, we detected a fibroblast growth factor receptor 2 (FGFR2) mutation in one of the cases. We reviewed the literature and present the clinical and morphological characteristics that must be considered along with other findings to accurately achieve the correct diagnosis, in correlation with the results of the ancillary technique. In conclusion, routine cytological specimens can be successfully used to perform additional investigations and support cytodiagnosis in difficult cases.

A skin tumor from an orthopedic oncology perspective: Pilomatrixoma in extremities (11 years experience with 108 cases)

Pilomatrixoma, also known as calcifying epithelioma of Malherbe, is a benign skin neoplasm originating from hair follicle matrix cells. Pilomatrixoma is a common skin neoplasm that is often misdiagnosed as another type of skin condition. The aim of our study is to review 11 years' worth of experience in examining clinical and histopathological presentations, imaging findings, management approaches, and treatment outcomes of pilomatrixoma at a tertiary hospital. A review of the pathology database revealed that 108 extremity pilomatrixomas were excised between 2007 and 2018. Hospital charts, and pathology and orthopedic clinic records, were reviewed for patient data such as age, gender, clinical and histopathological presentations, preoperative diagnosis and imaging results, management approach, recurrence, and treatment outcomes. The main presenting symptom was a hard, subcutaneous, slowly growing mass. The preoperative diagnosis was accurate and consistent with the pathological diagnosis of pilomatrixoma in only 35 cases (32%). The optimal diagnostic tool for pilomatrixoma seems to be ultrasound imaging of superficial tissue, and the optimal first-line treatment might be surgical excision with clear margins. However, pilomatrixoma is a benign tumor, with atypical forms, and there no tumor-specific diagnostic tool is available other than careful histopathological examination.

Metastasizing Malignant Granular Cell Tumor (Abrikossoff Tumor) of the Anterior Abdominal Wall, with Prolonged Survival

Malignant granular cell tumor (MGCT) is a rare high-grade mesenchymal tumor of Schwann cell origin. MGCTs commonly affect thigh, extremity, and trunk; however, involvement of the abdominal wall is quite rare. It has poor prognosis with 39% mortality rate in 3-year interval. We report a 50-year-old female who had MGCT arising in the anterior abdominal wall and developed massive metastatic deposits in both lungs and in the right inguinal lymph nodes, with prolonged survival for 11 years. A brief review of the literature is presented.

Importance of Individual Ghost Cells in Fine-Needle Aspiration Cytology Diagnosis of Pilomatricoma

Background

Although histological diagnosis of pilomatricoma is not difficult because of its unique histological features, cytological diagnosis through fine-needle aspiration cytology (FNAC) is often problematic due to misdiagnoses as malignancy.

Methods

We reviewed the cytological features of 14 cases of histologically-proven pilomatricoma from Korea Cancer Center Hospital, with a discussion on the diagnostic pitfalls of FNAC.

Results

Among 14 cases of pilomatricoma, 10 (71.4%) were correctly diagnosed through FNAC, and two (14.3%) were misdiagnosed as carcinoma. Cytologically, all cases had easily recognizable clusters of basaloid cells and foreign body-type multinucleated cells. Although ghost cells were also found in all cases, some were inconspicuous and hardly recognizable due to their small numbers.

Conclusions

An accurate diagnosis of pilomatricoma in FNAC is feasible with consideration of clinical information and close examination of ghost cells.

Complicated Giant Pilomatrixoma of the Parotid Region

OBJECTIVE

Pilomatrixoma (calcifying epithelioma of Malherbe) is a benign soft tissue tumour arising from dermis or subcutaneous tissue which should be considered in differential diagnosis of preauricular lesions especially when skin fixation is present.

CASE REPORT

Twenty-three year old male referred to our clinic with complaint of left preauricular swelling over 18 months which enlarged and became painful in the last 2 months. Because the lesion showed signs of infection, surgery was planned after medical therapy was completed. FNAB suggest pleomorphic adenoma as preliminary diagnosis. US or MRI showed no specific feature.

TREATMENT AND PROGNOSIS

Total excision, superficial parotidectomy with facial nerve sparing was performed after regression of infectious signs. Postoperatively no recurrence was detected.

CONCLUSION

Pilomatrixomas are benign tumours but have diagnostic difficulties according to clinical and cytologic findings. This rare lesion should be kept in mind to avoid misdiagnosis as malign parotid tumours, particularly in the presence of skin change.

Giant pilomatrixoma presenting in the posterior thorax, a rare location and the largest described

Pilomatrixoma is a common benign soft tissue neoplasm arising from hair follicle cells, typically not exceeding 3 cm and located mainly within the head and neck regions. Lesions greater than 3 cm or those located elsewhere are rare and are often not thought of or high on a differential diagnosis. Moreover, the radiographic features of pilomatrixoma are very nonspecific making the diagnosis even more difficult and rarely described in the radiology literature. We present the largest reported case of pilomatrixoma measuring 24 cm arising from the posterior thorax. Our hope is to increase awareness of this diagnosis for slow-growing soft tissue masses not located in the classically described locations of head and neck, explore the radiographic features on various imaging modalities, and review the current radiology literature.

Fine-needle aspiration cytology of pilomatrixoma: A short series of three cases

Pilomatrixoma (PMX) (pilomatricoma, calcifying epithelioma of Malherbe) is a benign tumor with differentiation toward the hair matrix cells and is common in head and neck region. It is most commonly seen in the first two decades of life and presents as a subcutaneous, small, asymptomatic firm solitary nodule. Fine-needle aspiration cytology (FNAC) has been described as an important preoperative diagnostic investigation though on cytology the diagnosis of PMX is sometimes difficult and misdiagnosed. We describe two patients with gradually increasing asymptomatic swelling on pinna and middle finger. FNAC was done and a diagnosis of PMX was given, further confirmed by histopathological examination. The present cases highlight the importance of FNAC in considering PMX as differential diagnosis of dermal or subcutaneous nodules in locations other than head and neck. Cytopathologists who play an important role in the preliminary diagnosis should keep in mind the variability of the cellular composition of these types of lesions to avoid misdiagnosis.

Pilomatrixoma masquerading as metastatic adenocarcinoma. A diagnostic pitfall on cytology

Pilomatrixoma (Px) is a relatively uncommon slowly growing, benign skin appendageal tumor with a wide morphological spectrum, and can pose diagnostic difficulties especially in cases with unusual clinical presentation. We report a case of young male who presented with a nodule over anterior abdominal wall, fine needle aspiration cytology (FNAC) revealed predominantly small cells in focal acinar pattern suggestive of metastatic carcinoma; however, histopathological diagnosis was Px. The case highlights the diagnostic pitfalls on cytology due to limited morphology.

An unusual presentation of giant pilomatrixoma in an adult patient

BACKGROUND

Pilomatrixoma (OMIM ID #132600) is a benign cutaneous tumor originating from the pilosebaceous follicle and characterized by the presence of subcutaneous nodules of up to 3.0 cm in diameter, usually on the head, neck and upper extremities. It is most common in the first two decades of life and after the age of 60.

MAIN OBSERVATIONS

An adult female patient was evaluated, presenting a solid tumoral lesion with erythematous surface and purplish tone, with approximately 7.5 x 5.0 cm in size, in the interscapulovertebral region. It was thought to be an epidermoid cyst, sarcoma, calcified hemangioma, giant dermatofibroma, or nodular basal cell carcinoma. The resection of the lesion was carried out and, at the histological examination, specific details were observed that led to the diagnosis of pilomatrixoma.

CONCLUSION

Pilomatrixoma should be suspected in the differential diagnosis of giant adnexal tumors.

Cytodiagnosis of pilomatrixoma from an uncommon site with unusual presentation

Pilomatrixoma or pilomatricoma is an uncommon benign tumor of hair matrix origin, which most commonly occurs in the head and neck region and upper extremities. In this study, we report a case of pilomatrixoma of a 35-year-old female presenting with left-leg swelling with surface ulceration, clinically thought to be malignant. Fine-needle aspiration cytology (FNAC) of the lesion showed clusters of basaloid cells with round to ovoid nuclei, nucleated squamous cells, and anucleated squames and clusters of shadow cells. Acytological diagnosis of pilomatrixoma was made. Subsequent surgical excision and histopathological examination confirmed the diagnosis. This case highlights a rare site of presentation and the role of FNAC in preoperative diagnosis of this benign tumor for proper management.

Limits of fine-needle aspiration cytology in diagnosing pilomatrixoma: a series of 25 cases with clinico-pathologic correlations

Background:

Pilomatrixoma (PMX) is a benign, quite uncommon, skin neoplasm, which is frequently misdiagnosed by clinicians.

Aim:

We have analyzed 25 PMX to determine the agreement between clinical diagnosis, preoperative FNA characteristics, and corresponding histopathological specimens; moreover, reliable cytologic criteria for PMX and the differential diagnosis to avoid cytological pitfalls have been emphasized.

Materials and Methods:

By fine-needle aspiration (FNA) cytology a series of consecutive cases of PMX collected during last 5 years were studied. Smears were stained by Papanicolau and May-Grünwald-Giemsa.

Results:

Patients affected by PMX were 11 males, 14 females (ratio 1:1.27); the mean age was 32.72 years with age range 3-78 years, being 72% (18/25) of patients 40 years or less. PMX was mainly distributed in the head-neck region (52%), scalp (16%), upper/lower arms (28%), and chest (4%). The observed diagnostic cytological features were represented by clusters of basaloid epithelial cells, shadow or ghost cells, inflammatory background, calcification, and giant cells. Unfortunately, not all these morphological aspects were always disclosed in smears, thus making the cytological preoperative diagnosis questionable and problematic.

Conclusions:

The experience of a well-trained cytopathologist should distinguish the relevant FNA features in terms of smear background, architecture, and cell morphology. The most dangerous mistake in FNA diagnosis of PMX regards a diagnosis of primary malignant or metastatic cutaneous lesions.

Giant pilomatricoma mimicking a malignant parotid mass

Pilomatricomas are benign neoplasms of the hair follicle occurring relatively often in the pediatric population. However, lesions attaining massive proportions are very rarely encountered. We describe such a case presenting in the parotid region and initially misdiagnosed as malignancy. Preoperative biopsy provided accurate diagnosis and allowed definitive surgical excision using a parotid-sparing approach. In children, giant pilomatricoma should be included into the differential diagnosis of noninflammatory masses of the salivary gland region.

Cytologic features of microcystic adnexal carcinoma

Microcystic adnexal carcinoma (MAC) is an uncommon skin neoplasm with a predilection location around the lips. It is characterized by cords and nests of neoplastic cells forming ductular or glandular structures that are embedded in dense collagenous stroma. An eighty-seven year old Caucasian female patient presented with a painless, slowly enlarging mass measuring 3.3 × 2.7 × 1.0 cm on the lower lip for approximately 6 months. The patient underwent 2 fine needle aspiration biopsies (FNAs). Smears made from both FNAs demonstrated similar features including low cellular smears, three dimensional cell clusters forming a glandular structure, round to oval cells with high N:C ratio, occasional cytoplasmic lumens, without distinct hyperchromasia, focal inconspicuous nucleoli, smooth regular nuclear membranes, abundant naked nuclei, occasional squamoid cells and focal acellular stromal fragments in the background. The cytologic differential diagnosis included skin adnexal carcinoma and low grade mucoepidermoid carcinoma arising in the minor salivary gland. The mass was subsequently excised. The diagnosis of microcystic adnexal carcinoma was made. We report cytologic features of MAC and also suggest that MAC can possibly be diagnosed by FNA with the appropriate clinical vignette and immunohistochemical profile..

Pilomatrixoma in an infant: diagnostic challenges of fine-needle aspiration

Fine-needle aspiration biopsy (FNAB) is a well-recognized minimally invasive tool in the diagnosis of neoplasia of various organ systems. Several reports in the literature suggest that FNAB can be an accurate method for the preoperative diagnosis and treatment planning. We describe a case to caution the interpretation from a FNAB that contains suboptimal contents (basaloid cells only) and highlight a clinical-pathologic-based algorithm that can provide the appropriate management for the patient when the cytopathologic diagnosis does not fit the clinical impression.

Pilomatricoma: Experience of the Hospital for Sick Children

Background

Pilomatricoma (calcifying epithelioma of Malherbe) is a common skin neoplasm in the pediatric population that is often misdiagnosed as other skin conditions or tumours.

Objectives

The objective of the present retrospective study was to review the clinical and histopathological presentation of this neoplasm in children.

Methods

The records of the pathology department at The Hospital for Sick Children, Toronto, Ontario, were searched for all cases of pilomatricoma between 2001 and 2006. The records of these patients were reviewed to determine sex, age, location and size of the tumour, pathological features and recurrence rate. All patients underwent surgical excision of the lesions.

Results

A total of 93 lesions in 85 patients were identified. The median age was 8.7 years. Of the 85 patients diagnosed with pilomatricoma, 44 (52%) were female. In all cases, the initial presentation was an asymptomatic, slow growing, superficial hard mass with bluish discolouration. The most common sites of occurrence were the face (48%), neck (21%) and upper limbs (18%). The size of the surgical specimens collected ranged from 0.1 cm to 2.6 cm. The diagnosis was confirmed by histopathological examination in all cases. Ghost cells and basaloid cells were described in most of the cases (83%). There were no recurrences in this series.

Conclusions

This entity should be considered with other benign or malignant conditions in the clinical differential diagnosis of solitary firm skin nodules, especially those on the face, neck and upper limbs. The diagnosis can generally be made by clinical examination. The treatment of choice is surgical excision, and the recurrence rate is very low.

Pilomatricoma in childhood: a retrospective study from three European paediatric centres

Pilomatricoma is characterised as a common, slowly growing benign cutaneous tumour that appears generally within the first decades of life. The clinical diagnosis is frequently missed, especially by the paediatrician unfamiliar with these tumours. We present the experience gained in three European tertiary care paediatric centres with the treatment of pilomatricoma and also current data on the aetiology, clinical presentation and management. A retrospective study was carried out in 83 patients suspected for pilomatricoma during a 7-year period (1996-2002) at the departments of Paediatric Surgery of the Children's University Hospital "Federico II", Naples, Hospital "San Bortolo", Vicenza and "Aghia Sophia" Children's Hospital, Athens. The age range was from 10 months to 17 years, median age 8 years. All patients were treated by surgical excision and all specimens were examined by histopathological assessment. The follow-up varied from 5 months to 6 years. The correct diagnosis was made preoperatively in 68 patients (82%). The female/male ratio was 2:1. The sites of occurrence were the head (47.5%), especially in the periorbital region, the neck (9%), the upper limbs (35.5%), the inferior limbs (4%) and the thorax (4%). Each patient exhibited a single pilomatricoma except for two patients who had multiple lesions (2.4%). One of them had Steinert disease (myotonic dystrophy). No recurrences were observed during the follow-up period.

CONCLUSION

Pilomatricoma is one of the most common cutaneous adnexal neoplasms in children. Surgical excision including clear margins and its overlying skin in most cases is the treatment of choice. The recurrence as well as malignant evolution is rare.

Pilomatrixoma: a diagnostic pitfall in fine-needle aspiration biopsies. A review from a small county hospital

A 10-year-old Hispanic girl presented with a 3-cm mass over her right parotid region. A fine-needle aspiration (FNA) was performed and the preliminary and final diagnoses were "suspicious for carcinoma, possible mucoepidermoid carcinoma." A subsequent computed tomography demonstrated an extra-parotid lesion attached to the skin. The FNA smears were reviewed and the diagnosis of a pilomatrixoma (PMT) was reached. The lesion was excised and the diagnosis of benign PMT confirmed. Pilomatrixomas are uncommon skin adnexal tumors most commonly found in the head and neck area of young adults and children. In 10 years there were 16 PMTs among 60,280 surgical pathology specimens in the pathology files of our 300-bed general county hospital. Pilomatrixoma is recognized as a diagnostic pitfall not only clinically but also on FNA cytology. On the physical examination, the bluish skin discoloration over the lesion so typical of PMT was overlooked. On FNA, the basaloid cells of PMT were mistaken for intermediate cells of mucoepidermoid carcinoma. The presence of anucleated squames was not properly recognized. These are usually absent in mucoepidermoid carcinoma and represent a hallmark of PMT. This case illustrates well the risk of misdiagnosing a pre-auricular PMT as a malignant tumor of the parotid gland.

Pilomatrixoma: clinicopathologic study of 51 cases with emphasis on cytologic features

The clinical and pathologic features of 51 cases of pilomatrixoma found in our archives from 1990-1999 were reviewed, with emphasis on the cytopathologic features of the 22 cases that were sampled by fine-needle aspiration (FNA) biopsy prior to excision. Although uncommon, almost 20% of the pilomatrixomas in this series occurred in adults over age 30. Of the commonly reported features, the presence of basaloid cells and ghost cells in FNA smears, associated with a cutaneous location of the lesion, was sufficient for a confident cytologic diagnosis of pilomatrixoma. The presence of foreign body-type giant cells, nucleated squamous cells, and calcification, alone or in combination, was less specific, but supported a diagnosis of pilomatrixoma. Although infrequently reported, prominent nucleoli in basaloid cells and smears containing refractile keratin clumps were very useful clues in the diagnosis of pilomatrixoma. Finally, the routine use of cell blocks is recommended because in many of the cases presented ghost cells were fragmented or obscured in smears, but were more readily identified in cell block sections.