Pilomatricoma Diagnosed on Fine-Needle Aspiration Cytology in a Rare Setting of Celiac Disease: Averting a Misdiagnosis of Malignancy.

Dear Editor,

Pilomatrixoma (PMX), also known as “pilomatricoma” or “calcifying epithelioma of Malherbe,” is a slow-growing benign adnexal tumour which arises from pluripotential cells of the matrix and inner sheath of a normal hair follicle as well as hair cortex.[1] It is commonly located on head and neck region; with 60% of the cases arising in the first two decades of life neck with a slight female preponderance.[2] The treatment of choice is complete surgical resection.

A 6-year-old male child came to the out-patient department of our hospital with a subcutaneous swelling on the right submandibular region of two months duration. Detailed history revealed that the child was diagnosed with celiac disease at the age of 3 years which was based on the histopathology and raised serum tissue transglutaminase IgA levels. At present, he had already been investigated outside with fine-needle aspiration cytology (FNAC) where a diagnosis of a malignant round cell tumour was offered. A repeat FNAC was performed and the preparation stained with May-Grunwald-Giemsa (MGG) stain revealed cellular smears comprising of sheets of round blue cells giving basaloid appearance with high nuclear-cytoplasmic (N:C) ratio and evenly dispersed chromatin [Figure 1a] along with sheets of anucleate cells without definite nuclei resembling ghost cell population [Figure 1b]. On examining the Papanicolaou stained smears, the eosinophilic cells devoid of a definite nucleus imparting an anucleate squamoid appearance were appreciated. The background shows randomly scattered multinucleate giant cells. On collating the clinical presentation and cytomorphological findings, a diagnosis of a benign adnexal tumor with follicular differentiation; suggestive of a Pilomatricoma was given. The lesion was excised and sent for histopathological examination. Histology revealed an intact epidermis overlying a lobulated neoplasm in the dermis which exhibited cellular heterogeneity comprising of nests of blue appearing basaloid cells alongside eosinophilic cell population having ghost appearance [Figure 2]. The morphology was consistent with a Pilomatricoma.

Figure 1

(a) Cellular smear showing high N: C ratio basaloid cells lying in tight cohesive clusters (MGG, ×100). (b) High power magnification showing sheet of shadow cells with defined cellular outlines devoid of nuclei (MGG, x400)

Figure 2

Histomorphology revealing the classical constituents of basaloid and shadow cells (Haematoxylin and Eosin, x100)

This emphasizes the need of the cytopathologists to be aware of such an indolent entity which shares and can have overlapping cytological features with malignancies such as squamous cell carcinoma, basal cell carcinoma, rhabdomyosarcoma, merkel cell carcinoma, small cell carcinoma.[3] An attempt to identify this benign lesion correctly on FNAC can avert unnecessary radical treatment and prevent therapy related morbidity.

The association of multiple pilomatricomas with celiac disease has been documented in the literature.[4] The etiopathogenesis of the pilomatricomas has been related to mutations in the CTNNB1 gene, responsible for encoding beta-catenin.[5] This case highlights the unique though rarely described causal association between these two entities and emphasizes the need to reinstate the role of cytological examination in reaching the correct diagnosis aimed at guiding the clinician for further management.

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