Basaloid squamous cell carcinoma.

CLINICAL FEATURES

A 56-year-old male patient reported with the chief complaint of ill-fitting lower dentures. The patient was habituated to tobacco and pan chewing for the past 30 years. On clinical examination, a proliferative verrucous growth was noticed in the lower anterior region, extending from 33 to 43 and crossing the midline. The lesion was firm in consistency and nontender.

HISTOPATHOLOGY

Superficial parakeratinized stratified squamous surface epithelium is seen invading the underlying connective tissue [Figure 1].

Figure 1

Surface epithelium showing invasion into the connective tissue (H and E, ×4)

The connective tissue stroma shows strands and islands of neoplastic epithelial cells. These islands show peripheral palisading basaloid-appearing cells with hyperchromatic nuclei, scanty cytoplasm, and central comedo-like necrosis [Figures 2–5].

Figure 2

Infiltrating strands of tumor epithelial cells showing keratin pearl formation and mitotic figures (H and E, ×10)

Figure 5

Tumor islands showing palisaded arrangement of peripheral basaloid cells (H and E, ×40)

Keratin pearl formation and mitotic figures are evident in the infiltrating strands [Figure 6].

Figure 6

Photomicrograph showing mitotic figures and nuclear and cellular atypia (H and E, ×40)

There is a squamous cell component interspersed among the basaloid islands.

The stroma shows chronic inflammatory cell infiltration.

Islands showing peripheral palisading of basaloid cells (H and E, ×10)

Tumor islands showing comedo-like necrosis (H and E, ×10)

DIFFERENTIAL DIAGNOSIS

Basal cell carcinoma

Adenoid cystic carcinoma (solid variant)

Adenosquamous carcinoma

Basal cell adenocarcinoma

Salivary duct carcinoma

Neuroendocrine carcinoma

Adenoid cystic carcinoma (solid type)

Neoplastic myoepithelial and ductal cells are present.

Groups of cuboidal cells are seen, with dark nuclei and little tendency towards duct or cyst formation.

Squamous cell component and keratin pearl formation is absent.

Tumor cells show a swirling arrangement around the nerve bundles, indicating perineural invasion.

Adenosquamous carcinoma

Surface squamous cell component and deeper glandular component are more distinct.

Glandular structures are lined by basaloid, columnar, or mucin-secreting cells.

Intracytoplasmic mucin demonstrated by mucicarmine staining helps to differentiate this from the variants of squamous cell carcinoma that show a pseudoglandular pattern of differentiation.

Basal cell carcinoma

Nests of uniform-appearing tumor cells with scanty cytoplasm and large hyperchromatic oval nuclei, which shows peripheral palisading.

Increased mucin is present in the surrounding stroma, with cleft artifact occuring between tumor nests and surrounding stroma because of shrinkage of mucin during fixation and staining.

Pseudoglandular change and pigmented variants are noted occasionally.

Basal cell adenocarcinoma

Two forms of epithelial cells are seen, usually intermingled with each other – small round cells with scanty cytoplasm and dark basophilic nuclei and large polygonal cell with pale basophilic cytoplasm.

For the diagnosis of carcinoma there should be more than 4–5 mitotic figures per 10 high-powerfields.

Basal cell ameloblastoma

Islands of odontogenic epithelium lined peripherally by basaloid cells that tend to be cuboidal rather than columnar, surrounding central nests of uniform basaloid-appearing cells.

Absence of central comedo necrosis and any squamous component.

Salivary duct carcinoma

Tumor islands with large central cystic spaces with comedo type of necrosis and a several-cell-layers-thick peripheral rim of tumor cells that are cuboidal/polygonal and have a moderate amount of eosinophilic cytoplasm.

Perineural and perivascular invasion is common.

FINAL DIAGNOSIS

Basaloid squamous cell carcinoma