Abstract
Background
Pilomatricomas are benign skin tumors originating from hair matrix cells in the dermal layer of the skin, especially in the head and neck region. They may mimick malignant lesions on fine-needle aspirate cytology.
Methods
This is a case report of a pilomatricoma of the cheek which was initially diagnosed as squamous cell carcinoma on fine-needle aspirate cytology. As part of the staging work-up, a PET/CT scan was performed, revealing a FDG-avid superficial cheek lesion and also an ipsilateral FDG-avid level II cervical lymph node, giving the impression of metastatic squamous cell carcinoma.
Results
The cheek lesion, as well as the cervical lymph node was excised. The final histology showed benign pilomatricoma and reactive lymphadenopathy.
Conclusion
Pilomatricoma should be considered as an uncommon differential diagnosis for an FDG-avid cutaneous lesion on PET/CT, even in the presence of ipsilateral FDG-avid cervical lymphadenopathy.
1
Introduction
Pilomatricomas are benign skin tumors originating from hair matrix cells. They usually occur in the first two decades of life, although cases presenting beyond the fourth decade of life are not uncommon . Pilomatricomas present as a single slow-growing, painless, superficial mass arising from the dermal layer of the skin, over the hair-bearing areas of the body, especially the head and neck. Other less common locations include the upper limbs, trunk and lower limbs, with the exception of the palms and soles. The overlying skin may have a bluish discoloration and may exhibit the ‘tent sign’, where stretching of the skin accentuates the nodular appearance of the mass .
A clinical diagnosis of pilomatricoma is difficult as many cutaneous lesions, including sebaceous cyst, epidermal cyst, and dermoid cyst have similar clinical characteristics. Cytological diagnosis by fine needle aspirate (FNA) biopsy is also a challenge, with up to 45% of cases incorrectly diagnosed . Although cytologic findings of ghost (shadow) cells and basaloid cells are pathonogmic of pilomatricoma, ghost cells may not always be present, and a predominance of basaloid cells may be mistaken for basal cell carcinoma or basaloid squamous cell carcinoma . Other cellular components may be present, including foreign body giant cells, calcium deposits and keratin debris, hence adding to the complexity of diagnosis.
While there has been increasing utilisation of combined positron emission tomography and computed tomography (PET/CT) scans as part of staging and work-up for head and neck malignancies, very few cases of F-18 fluoro-2-deoxyglucose (FDG) uptake by pilomatricoma have been reported . In these cases, PET/CT was performed because of suspected malignancy based on FNA cytology findings of poorly differentiated carcinoma (2 cases) and squamous cell carcinoma (1 case).
Here we report a unique case of benign pilomatricoma with lymphadenopathy, which was mistaken for metastatic malignancy based on FNA cytology and PET/CT findings. This would be the first report of FDG-avid pilomatricoma with FDG-avid lymphadenopathy in the literature.
2
Case report
A 61 year old Chinese female presented with a painless lump over her left cheek, gradually enlarging over a duration of four months. On physical examination, a firm, subcutaneous nodule was felt over the posterior aspect of the left mandible measuring 2.5 cm. A thorough head and neck examination including nasoendoscopy was performed and did not reveal any other suspicious lesion. There was also no palpable cervical lymphadenopathy.
A FNA biopsy of the lesion had previously been performed in another institution, and reported as suspicious for poorly differentiated squamous cell carcinoma. Microscopic examination of the smears and cell-block was reported as aggregates of crowded abnormal cells with thick cytoplasm, and organophilic staining with PAP stain.
In view of the cytology report, a PET/CT scan was arranged at our institution, and the mass showed a standardized uptake value (SUV) of 15.9 ( Fig. 1 A ), suspicious for malignancy. Furthermore, the PET/CT scan revealed a left level II lymph node measuring 1.5 × 1.2 cm, with an SUV of 4.1 ( Fig. 1 B). The case was discussed at the multi-disciplinary tumor board, and the impression was that of metastatic squamous cell carcinoma. A decision was made for surgical resection of the left cheek lesion with frozen section, possible left selective neck dissection, and post-operative radiation therapy, should malignancy be confirmed.
2
Case report
A 61 year old Chinese female presented with a painless lump over her left cheek, gradually enlarging over a duration of four months. On physical examination, a firm, subcutaneous nodule was felt over the posterior aspect of the left mandible measuring 2.5 cm. A thorough head and neck examination including nasoendoscopy was performed and did not reveal any other suspicious lesion. There was also no palpable cervical lymphadenopathy.
A FNA biopsy of the lesion had previously been performed in another institution, and reported as suspicious for poorly differentiated squamous cell carcinoma. Microscopic examination of the smears and cell-block was reported as aggregates of crowded abnormal cells with thick cytoplasm, and organophilic staining with PAP stain.
In view of the cytology report, a PET/CT scan was arranged at our institution, and the mass showed a standardized uptake value (SUV) of 15.9 ( Fig. 1 A ), suspicious for malignancy. Furthermore, the PET/CT scan revealed a left level II lymph node measuring 1.5 × 1.2 cm, with an SUV of 4.1 ( Fig. 1 B). The case was discussed at the multi-disciplinary tumor board, and the impression was that of metastatic squamous cell carcinoma. A decision was made for surgical resection of the left cheek lesion with frozen section, possible left selective neck dissection, and post-operative radiation therapy, should malignancy be confirmed.
