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

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.

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.

Cytomorphological spectrum of pilomatricoma - A series of 28 cases

BACKGROUND

Pilomatricoma is a benign tumour that originates in the outer sheath of the hair follicle root. The clinical diagnosis of this rare entity is often missed, possibly due to a lack of awareness. Its characteristic cytomorphological features are sheets of ghost cells, basaloid cells, calcification and foreign body giant cell reaction. However, the above features may not all be present in all cases, rendering cytological diagnosis difficult.

MATERIALS AND METHODS

This retrospective study included all cases of pilomatricoma diagnosed on fine needle aspiration over a period of 4 years. The histopathological diagnosis was retrieved for the cases wherever possible. A detailed histopathological and cytological evaluation was performed for the various components-basaloid cells, ghost cells, calcified debris, foreign body giant cells, bare nuclei, neutrophils, and macrophages-and they were graded on a scale of 0 to 3+.

RESULTS

The 28 cases included 8 female and 20 male patients with a mean age of 34.6 years. Most cases (22 cases; 78.6%) were located in the head and neck, with the scalp being the most common site. Twenty-five cases were cytologically diagnosed as pilomatricoma based on a variable admixture of the various components-nests of basaloid cells, ghost cells, foreign body giant cell reaction, calcified debris and viable squamous cells. However, in two cases which showed an absence of basaloid cells, a differential diagnosis of epidermal inclusion cyst was also included. Another case showed a predominance of basaloid cells with a paucity of ghost cells, so a differential diagnosis of adnexal tumour was also included. Among all the cytological parameters, sheets of ghost cells followed by nests of basaloid cells and foreign body giant cell reaction had the highest sensitivity in the cytological diagnosis of pilomatricoma.

CONCLUSION

The presence of sheets of ghost cells is the most sensitive parameter for the cytological diagnosis of pilomatricoma. It is important that pilomatricoma should be considered in the differential diagnosis of subcutaneous masses, particularly in the head and neck region.

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 retrospective comparison of salivary gland fine needle aspiration reporting with the Milan system for reporting salivary gland cytology

BACKGROUND

Fine needle aspiration (FNA) is a routine sampling method in the diagnostic work up of salivary gland lesions. Despite universal use, no standardised classification existed for the cytopathological reporting of such entities until recently. The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) aims to standardise the reporting of these lesions, offering risk of malignancy rates and clinical management recommendations.

METHODS

We retrospectively applied MSRSGC to cases reported over a 5-year period. Salivary FNA specimens were reclassified according to the MSRSGC as (I) non-diagnostic, (II) non-neoplastic, (III) atypia of undetermined significance (AUS), (IV) benign neoplasm and salivary gland neoplasm of uncertain malignant potential, (V) suspicious for malignancy, and (VI) malignant. Cases with surgical resections were documented and risk of malignancy calculated for each group, where possible. We compared our outcomes with similar studies performed since publication of the Milan criteria.

RESULTS

In total, 192 specimens were reassigned as non-diagnostic (n = 30), non-neoplastic (n = 31), AUS (n = 1), benign neoplasm (n = 97) and salivary gland neoplasm of uncertain malignant potential (n = 4), suspicious for malignancy (n = 3), and malignant (n = 26). There were 73 surgical resections. Our calculated risk of malignancy was within the proposed MSRSGC rates for the non-diagnostic, benign neoplasm and malignant groups. One AUS case did not undergo surgery. Benign and malignant sensitivities and specificities for the original reporting categories were 88.24% and 95.72%, and 100% and 95.45% for the MSRSGC, respectively.

CONCLUSION

Salivary gland FNA has high diagnostic accuracy and the MSRSGC offers standardised reporting and assistance in the stratification of cases. This may improve communication between pathologists and clinicians with improved outcomes for patients.

Cyto-Histopathological Correlation of Skin Adnexal Tumors: A Short Series

Background:

Skin adnexal neoplasms are relatively rare and thus uncommonly encountered in routine pathology practice.

Aims:

The present study was conducted with the aim to diagnose various skin adnexal tumors on fine-needle aspiration cytology (FNAC) followed by confirmation on histopathology and immunohistochemistry of the excised tumor.

Materials and Methods:

A total of 11 cases of superficial nodular swellings of the skin were studied over a period of 2 years from 2015 to 2016. FNAC of the swelling was performed and slides were stained with Giemsa stain. Following FNAC, the swelling was excised and subjected to histopathological examination. Immunohistochemistry was performed in some cases for confirmation.

Results:

It was observed that overall incidence of adnexal tumors (ATs) encountered on FNAC was very low. Typing of ATs on cytology was possible in 82% cases (9/11 cases) with diagnostic accuracy of 88% (8/9 cases). Most common tumor encountered in the study was nodular hidradenoma followed by pilomatrixoma, trichoepithelioma, cylindroma, chondroid syringoma, and trichilemmal cyst. Majority of the cases were benign except one case, which subsequently turned malignant.

Conclusion:

FNAC is a simple, safe, and cost-effective tool in diagnosing skin ATs. Cytological diagnosis of these lesions is depends on clinical correlation and cytomorphological features. FNAC in lesions suspected to be malignant can guide the surgeon regarding extent of excision.

Pilomatrixoma: A Comprehensive Review of the Literature

INTRODUCTION

Pilomatrixoma, also known as calcifying epithelioma of Malherbe, is a superficial benign skin tumor that arises from hair follicle matrix cells. Although pilomatrixomas are well-recognized lesions, clinically they are frequently misdiagnosed as other skin conditions. By reviewing all the literature over the past 10 years, the aims of this article are to analyze the cause, clinical presentation, management, and outcome of pilomatrixoma among children and adults to gain a more complete understanding of this lesion in today's clinical context.

METHODS

A MEDLINE and EMBASE search was conducted from January 2005 to February 2015 using a combination of the terms: "child," "childhood," "adult," and keywords: "pilomatrixoma," "pilomatricoma," and "calcifying epithelioma of Malherbe." A total of 150 articles were reviewed.

RESULTS

The lesions occurred most commonly in the first and second decades (mean age 16 years and 7 months). The commonest presentation was of an asymptomatic, firm, slowly growing, mobile nodule. Only 16% were accurately diagnosed on clinical examination. Imaging in the form of ultrasound, computed tomography, and magnetic resonance imaging has been reported. Pathological diagnosis was achieved through incision, punch, and shave biopsies. Pathological findings are discussed and summarized in this review.

CONCLUSION

Pilomatrixomas are thought to arise from mutation in the Wnt pathway and has been linked to several genetic conditions. It is commonly misdiagnosed preoperatively; however, with better awareness of the lesion, it can be appropriately treated while avoiding unnecessary diagnostic tests. Complete surgical excision with clear margins is almost always curative.