Basaloid Squamous Cell Carcinoma (BSCC) is an unusual and high grade variant of Squamous Cell Carcinoma (SCC) with a predilection for the upper aerodigestive tract. The cytopathologic diagnosis of basaloid squamous cell carcinoma can be problematic as there are several components of the differential diagnosis that share common cytomorphologic features [1,2]. Due to the presence of adenoid cystic-like features (cribriform pseudoglandular lumina with hyaline materials) in basaloid squamous cell carcinoma, it can mimick adenoid cystic carcinoma in FNA smears. This makes the cytological diagnosis of BSCC is problematic as only a few case reports and a rare case series have described the cytomorphology of BSCC [1,3-5]. However, a careful examination of the cytology can help in delivering a diagnosis of BSCC. In this case report we present the FNAC findings of metastatic BSCC in cervical lymph node of a 63-year-old male who presented with an mass lesion at the left tonsillar region.

Case report

63 year old male presented with change in the quality of voice voice and swelling in the left side of neck since one and half to two months. He also complained of difficulty in swallowing solid foods since one week. On examination left tonsillar region showed an irregular, nontender, hard mass. In addition there were multiple nontender, hard lymph nodes in the submandibular region. CT scan revealed a mass in the left tonsil measuring 3×2.9×2.8 cms (Figure 1) with multiple foci of calcification and left submandibular lymphadenopathy. Imprint smears from left tonsillar region revealed scanty material with only a few malignant cells. However FNA smears from left submandibular lymph nodes showed cellular smears comprising of numerous multilayered dense cell cultures and cup shaped fragments composed of pleomorphic tumor cells with overlapping irregular hyper chromatic nuclei, inconspicuous nucleoli, focal nuclear molding/acinar pattern and scanty basophilic cytoplasm. Conspicuous hyaline spherical globules of variable size with adherent tumor cells were seen (Figure 2). Some of the tissue fragments also revealed finger like cords of hyaline stroma (Figure 3). Metastatic carcinomatous deposits in the lymph node possibly from an adenoid cystic carcinoma of the tonsil was suggested. Tonsillar growth along with submandibular lymph node was excised and sent to us for histopathological examination. Microscopic examination of tonsillar growth revealed basaloiad squamous cell carcinoma revealing many foci of adenoid cystic like areas with microglandular/cribriform pattern contain eosinophilic secretions (Figure 4). Submandibular lymphnode (level 2) also revealed metastatic tumor deposits IHC.

Figure 1: CT Scan Revealing a Mass in the Left Tonsillar Region

Figure 2: FNA Smears Revealing Variably Sized Hyaline Globules Amongst Tumor Cells (Giemsa, 40x)

Figure 3: Photomicrograph Showing Finger Like Cords of Hyaline Stromal Material Between Tumor Cells (Giemsa, 40x)

Figure 4: Basaloid Squamous Cell Carcinoma Revealed Cribriform Arrangement of Tumor Cells With Eosinophilic Material in the Lumen (H&E, 40x)

In 1986 Wain et al. [6], first described the BSCC as a discrete and aggressive variant of SCC with a predilection to occur in the upper aerodigestive tract. Tonsil is a rare site for Basaloid squamous cell carcinoma [7]. The histological diagnosis of BSCC is uncomplicated as the histological features of BSCC have been adequately described. However, a cytological diagnosis of BSCC is problematic as only a few case reports and a rare case series have described the cytomorphology of BSCC [1,3-5]. The present case is unique because it mimicked adenoid cystic carcinoma due to presence of hyaline globules of variable size and finger like cords of hyaline stromal material between tumor cells which have not been described so far in basaloid squamous cell carcinomas.

Banks et al. [8] studied the cytologic features of metastatic basaloid squamous cell carcinoma in fine needle aspiration specimens from nine patients with primary tumors located in the base of the tongue, tonsil, epiglottis, nasopharynx, hypo pharynx and false vocal cord. The FNAC smears consisted of cohesive fragments and singly scattered small cells with scant cytoplasm, fine granular chromatin and inconspicuous nucleoli. Nuclear moulding, foci of necrosis, pseudo-glandular spaces, single keratinized cells and stromal material were also noted.

One of the cases of basaloid squamous cell carcinoma in their series had been interpreted elsewhere as an adenoid cystic carcinoma because of the presence of pseudo glandular structures with stromal cores. In addition, some authors also described the presence of metachromatic stromal material in the background [3]. In the present case there were hyaline globules of variable size and finger like cords of hyaline stromal material between tumor cells. 

The cytological differential diagnoses of BSCC comprises of tumors having small basaloid cells like BCC, Adenoid Cystic Carcinoma (ACC), Small Cell Undifferentiated Carcinoma (SCUC) and pilomatricoma [1,3,9]. Both BCC and BSCC show presence of clusters of small basaloid cells but in BSCC the cells show nuclei with clumped chromatin and prominent nucleoli along with mitoses and necrosis which are absent in BCC. ACC shows presence of pseudoglandular spaces and cribriform sheets of cells enclosing metachromatic hyaline stroma which may also be seen in BSCC but ACC lacks the squamous differentiation which is seen in BSCC [1]. Cytology smears of SCUC may show the presence of nuclear moulding but there is absence of squamous differentiation and hyalinized stromal fragments which are a feature of BSCC [3]. The clinical presentation of pilomatricoma is different from that of BSCC but it may be considered in the cytological differential diagnoses because of the presence of basaloid cells. The presence of ghost cells, calcification and multinucleation makes the differentiation of pilomatricoma uncomplicated.

A number of head and neck tumors show stromal hyaline globules, which includes membranous and trabecular variant of basal cell adenomas,pleomorphic adenoma, epithelial myoepithelial carcinoma, polymorphous low grade adenocarcinoma, adenoid cystic carcinoma.

In addition to these tumors basaloid squamous cell carcinoma can also show stream hyaline globules as in the present case and should be included in the differential diagnosis of head and neck tumors showing stream hyaline globules on FNA. A diagnosis of tumor must not be based solely on the presence of hyaline globules but requires a close scrutiny of cellular and nuclear features. 

BSCC is characterized histologically by presence of irregular nests of small basaloid cells interspersed with mucin filled cystic spaces and foci of squamous differentiation. Hyalinisation of stroma, comedonecrosis and foci of keratinization may also be noted. Adenoid cystic-like features (cribriform pseudoglandular lumina with hyaline materials) are also found [3]. In the present case the histological features were characteristic of BSCC with extensive adenoid cystic like areas. Hence a final diagnosis of BSCC was given. Immunohistochemistry may aid in the diagnosis of BSCC, it shows positivity for EMA which is negative in BCC. BSCC and ACC may be distinguished with use of p63 immunostaining, which is a specific and accurate marker. BSCC shows diffuse p63 positivity, while ACC display a compartmentalized pattern within tumor nests [10]. In addition, Strong expression of CD117 and/or DOG1 favors ACC [11].

Although the cytologic features of basaloid squamous cell carcinoma may mimic those of adenoid cystic carcinoma in fine needle aspiration specimens, they are sufficiently distinctive that a diagnosis of this variant of squamous cell carcinoma can be suggested for a patient whose primary neoplasm is located in the upper aerodigestive tract.

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