Pilomatrixoma: Misdiagnosed as a round cell tumor of soft tissue on fine needle aspiration cytology

Childhood pilomatrixoma mimicking malignant small round blue cell tumor with positivity for CD99: Potential pitfall in cytology

Pilomatrixoma is a relatively rare benign skin appendageal tumor, often presenting in the pediatric age group as a nodular lesion and most commonly involving the head and neck, making it amenable to primary fine needle aspiration (FNA) diagnosis. We report the clinical and histopathological findings of two cases of pilomatrixoma in children, both of which were initially misdiagnosed as small round blue cell tumors due to high cellularity and misinterpretation of the proliferating basaloid cells. Histopathology revealed basal cell proliferation and mitoses indicating that they were progressive, early lesions. The first case showed membranous positivity for CD99 which prompted a diagnosis of Ewing sarcoma. Awareness of the morphological spectrum including positivity for CD99 and careful evaluation of cell block histology could have averted the misdiagnosis. Pilomatrixoma should be included as an important differential diagnosis when faced with primitive-appearing cells on FNA, especially in children with mass lesions in the head and neck region.

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.

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.

Cytopathologic features of an unusual case of multiple eccrine spiradenomas misdiagnosed as a malignant round cell tumor

A 28-year-old lady presented with multiple swellings in her left shoulder, associated with intermittent pain since last one and a half years. Radiologic imaging revealed multiple, well-defined, subcutaneous lesions in her left supraclavicular region. Fine needle aspiration cytology (FNAC) smears were initially reported as Ewing sarcoma, elsewhere. On review, the smears showed cohesive clusters of round-to-oval cells with scant cytoplasm, which were focally arranged in an acinar-rosetting pattern around hyaline “droplets/bodies,” along with few scattered lymphocytes against a background of red blood cells. The diagnosis considered was adnexal tumor. Subsequent biopsy from the multiple lesions confirmed the diagnosis of eccrine spiradenoma. By immunohistochemistry, tumor cells were positive for CK7, epithelial membrane antigen (focally), S100 protein, and tyrosine-protein kinase Kit(C-KIT) /Cluster of differentiation (CD117). This case underscores the value of FNAC in skin adnexal tumors and constitutes as the first case report of multiple eccrine spiradenomas, initially misdiagnosed as Ewing sarcoma. Literature review of similar reported cases with treatment implications are presented.

Seemingly insignificant, but crucial cytomorphological leads in diagnosis of pilomatricoma of parotid region

Pilomatricoma is a benign cutaneous appendegeal neoplasm which occurs as dermal nodule on head and neck region of children and young adults. Tumors pose a potential difficulty when diagnosed on fine-needle aspiration cytology. In this communication, we illustrate the cytomorphological features of pilomatricoma in a 38-year-female who presented with a nodule over the parotid region. Repeated aspirations of this nodule revealed low cellularity and cytology was hence inconclusive. The final diagnosis was made on histological examination and then retrospectively when those paucicellular cytological smears were analyzed again; showed features that could have driven the pathologist toward pilomatricoma. Familiarization and careful cytological examination under appropriate clinical conditions is warranted.

Fine needle aspiration cytology of pilomatrixoma

AIM

To delineate and characterize the cytomorphologic features of pilomatrixoma (PMX) helpful in correct diagnosis of the lesion on fine needle aspiration cytology (FNAC).

MATERIALS AND METHODS

Archival records of clinical findings, FNAC and histopathological reports of PMX cases were analyzed. Aspirate findings in 14 cases of PMX were correlated with detailed clinical data and subsequent histopathology on excisional biopsy. Different morphological findings were graded semiquantitatively from 0 to 3+.

RESULTS

The series showed female preponderance, with head and neck being the commonest site. Majority patients had a single tumor with mean size of 1.6 cm. Out of 14 biopsy proven cases of PMX, cytology findings revealed PMX in 7 cases on the basis of ghost cells, groups of basaloid cells, squamous cells in combination with multinucleated giant cells and calcium deposits in a background of debris. The main reasons for erroneous diagnosis were predominance of one component over the others and non-representative aspirated material.

CONCLUSIONS

The cytological features of PMX are characteristic and allow a conclusive diagnosis provided the smears are examined keenly bearing in mind the diagnostic traps that can mislead a cytopathologist.