Pilomatricoma mimicking small round cell tumor on fine needle aspiration cytology: a case report

Pitfalls in soft tissue cytopathology

Fine needle aspiration biopsy (FNAB) is a diagnostic modality for the evaluation of suspicious soft tissue masses. Despite its reasonable sensitivity, specificity and positive predictive value in differentiating benign from malignant neoplasms, the exact subtyping of the primary soft tissue tumours can be challenging. Certain tumours constitute "pitfalls" and add to the diagnostic challenge. This review provides a detailed account of the diagnostic challenges in soft tissue cytopathology, including pitfalls and, more importantly, the ways to overcome these challenges by integrating clinical details, key cytomorphological features and judicious application of ancillary techniques.

Cytomorphology of skin adnexal tumors and its correlation with histopathology in a tertiary care center

Objectives

Even though fine-needle aspiration cytology (FNAC) can be successfully used for describing the cytomorphology of skin adnexal tumors and can help in identification of them as benign or malignant, histopathology remains the gold standard in confirmation of diagnosis. Skin adnexal tumors are a large and diverse group and are relatively less commonly encountered in routine practice; hence, knowledge of cytological features of these lesions is crucial for their appropriate management. The present study aims to evaluate the cytomorphological features of skin adnexal tumors on FNAC smears and their correlation with the histopathology.

Material and Methods

This is a retrospective study of FNAC of 60 cases of subcutaneous and dermal swellings over a period of 4 years from August 2018 to August 2022 in a tertiary care center.

Results

In the 60 cases of skin adnexal tumors evaluated, most cases were within the 2nd to 4th decade with male predominance. The FNA smears were helpful in picking up the nature of skin adnexal tumors, as in our case series, malignant lesions were 8.3% and benign were 91.7%. Majority adnexal lesions were of follicular or sebaceous differentiation. Histological diagnosis was available in 38 cases. Cytological diagnosis in 34 cases was concordant with histopathology. There was discrepancy observed in two cases which were reported as benign skin adnexal tumor but later turned out to be sebaceous carcinoma on histopathology.

Conclusion

Even though histopathology being the gold standard for confirmation of diagnosis, in the current era of minimally invasive procedures, FNAC stands out as a valuable modality and can be a promising alternative to diagnose skin adnexal tumors and understand their cytomorphology as the data are limited about it.

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.

Giant Sternal Pilomatricoma: An Unusual Tumor at an Uncommon Site

Pilomatricoma, pilomatrixoma, or calcified epithelioma of Malherbe is an uncommon, benign, isolated tumor of hair matrix primarily seen in children and young adults. The most common location is the head and neck region. It usually manifests as a small nodular mass. Here we report a rare case of giant pilomatricoma over the sternum in a 60-year-old male patient with an unusual clinical and radiological presentation mimicking a calcified sebaceous cyst.

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.

Diagnostic Evaluation of Skin Adnexal Tumors by Fine-Needle Aspiration Cytology

BACKGROUND

The diagnosis of skin adnexal tumors is usually based on histopathology. However, fine-needle aspiration cytology (FNAC) can be of great help and shows a high degree of correlation to the final diagnosis. It is helpful in many situations where skin lesions are a manifestation of certain systemic syndromes and aids to the formation of precise treatment plans.

MATERIALS AND METHODS

This prospective study was carried out to assess the diagnosis of skin adnexal tumors based on FNAC and their comparison with histopathological diagnoses. There were 14 patients with FNAC and histopathological follow-up in whom a final diagnosis of skin adnexal tumor was made. The results of FNAC were compared with histopathological diagnoses for complete correlation, partial correlation (cases where an FNAC diagnosis of skin adnexal tumor was made but a precise diagnosis of the subtype was not possible) or no correlation (where FNAC failed to diagnose a skin adnexal tumor).

RESULTS

Among the 14 cases of skin adnexal tumor, there was total correlation between the FNAC diagnosis and final histopathological diagnosis in 8 cases (57.1%) and a partial correlation in 4 cases (28.5%). There was no correlation of the FNAC diagnosis with the histopathological diagnosis in only 2 cases (14.3%).

CONCLUSIONS

FNAC is very useful in making a diagnosis of skin adnexal tumors and helps in the management of the patient.

Cytological and Immunocytochemical Features of Merkel Cell Carcinoma on Fine Needle Cytology Samples: A Study of 22 Cases

Merkel cell carcinoma (MCC) is an uncommon neuroendocrine small cell tumor derived from the transformation of the homonymous cells in the basal layer of the epidermis. MCC has a generally aggressive course, with a high tendency for local recurrence, lymph node involvement, and distant metastasis. Fine needle cytology (FNC) and immunocytochemistry were used as diagnostic procedures for 22 cases of MCC presented at our institute. All cases of MCC were successfully diagnosed on FNC. Among all of the monoclonal antisera used (CD56, CK20, CK MNF116, neuron-specific enolase (NSE), synaptophysin, and chromogranin), NSE and CD56 showed the highest frequency of positivity. The accuracy of the cytological diagnosis was 100% compared to the corresponding previous or subsequent pathological diagnoses. FNC and immunocytochemistry represent excellent and accurate diagnostic methods to distinguish MCC from other small-cell malignant entities.

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.

Pilomatrixoma of the arm: a rare case with cytologic diagnosis

Pilomatrixoma, a benign skin appendageal tumor, is seen commonly in head and neck. Occurrence of pilomatrixoma in the upper extremities is not common and has been reported infrequently in the available literature. Only a few cases with preoperative aspiration cytology have been reported in the literature. A five-year-old girl underwent fine needle aspiration (FNA) of a firm subcutaneous nodule on the lateral aspect of left arm. FNA smears showed scattered and few fragments of round to oval cells along with multinucleated giant cells. Few shadow cells were seen. A cytologic impression of pilomatrixoma was rendered, which was confirmed on histopathology. Pilomatrixoma, a common skin appendageal tumor in head and neck region, should be considered in the cytologic differential diagnoses of subcutaneous masses even in unusual locations like arm. The varied cytomorphology should be remembered to avoid misdiagnosis.

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.