Pilomatrixoma: a description of two cases diagnosed by fine-needle aspiration

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.

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.

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.

Fine-needle aspiration features of pilomatrixoma

BACKGROUND

Pilomatrixoma (PMX) is a benign skin neoplasm of hair matrix origin. The fine-needle aspiration (FNA) features of PMX frequently lead to a misdiagnosis of carcinoma.

METHODS

Nine cases of PMX in which a preoperative FNA was performed were reviewed. The cytologic features were compared with the histologic appearance of corresponding surgical specimens as well as with cytologic features of tumors that arose in the differential diagnosis.

RESULTS

Unequivocal benign diagnoses were rendered in three cases; the correct preoperative diagnosis of PMX was rendered in two of these cases and considered in an additional case. In four additional cases, carcinoma was diagnosed or could not be excluded. A noncommittal diagnosis of epithelial tumor, most likely of skin adnexal origin, was rendered in an additional single case. Retrospective review of the FNA smears in all nine instances disclosed cytologic features that corresponded well with the histologic components of PMX. Diagnostic cytologic features included cellular aspirates; clusters of small, primitive-appearing basaloid epithelial cells; a high nuclear-cytoplasmic ratio; evenly dispersed chromatin; prominent nucleoli; pink, fibrillary material enveloping clusters of basaloid cells; multinucleated giant cells; and sheets of ghost cells.

CONCLUSIONS

The FNA cytologic diagnosis of PMX may be extremely difficult; its distinction from various primary cutaneous carcinomas is most problematic. Recognition of a unique constellation of cytologic features in FNA smears in the appropriate clinical context is most helpful in making this distinction.

Fine needle aspiration (FNA) cytology of pilomatrixoma: report of 14 cases and review of the literature

We describe 14 cases of pilomatrixoma which were diagnosed preoperatively on FNA cytology. In contrast to the literature, our series showed male preponderance and some of the tumours in unusual locations such as thigh and breast. In three patients the tumours were larger than 5 cm. The clinical diagnosis varied from tumour not otherwise defined to sarcoma. The cytologic presentation had features which allowed a correct diagnosis in all cases and included basaloid cells surrounded by delicate pink fibres, shadow cells, giant cells, naked nuclei and calcium deposits. It is concluded that the FNA cytology of pilomatrixoma is characteristic and will allow a conclusive diagnosis even in cases with an aberrant clinical presentation.

Parotid fine-needle aspiration: a cytologic study of pediatric lesions

Fine-needle aspiration (FNA) of parotid lesions in the pediatric age group presents interesting diagnostic problems. There is limited cytologic literature available on the subject. We studied the cytologic findings on FNA of parotid masses in seven such cases. Patients ranged in age from 1 to 17 years (mean = 10.4). Diagnoses included lymphoepithelial cyst (n = 1), mucoepidermoid carcinoma (n = 2), pilomatrixoma (n = 1), acinic-cell carcinoma (n = 1), rhabdomyosarcoma (n = 1), and Ewing's sarcoma (n = 1). Six cases were confirmed by subsequent histologic examination. The study elaborates on the cytologic features of each lesion and discusses the differential diagnosis of closely related entities peculiar to this age group. It highlights the role of FNA as the diagnostic modality of choice in dealing with pediatric parotid masses.