Encyclopedia of Pathology

Living Edition
| Editors: J.H.J.M. van Krieken

Penile Basaloid Squamous Cell Carcinoma

  • Maurizio ColecchiaEmail author
  • Alessia Bertolotti
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-28845-1_4878-1


Basaloid carcinoma (BC) is an aggressive tumor composed of a monotonous population of small-to medium-sized cells with basophilic cytoplasm resembling basal cells (Cubilla et al. 1998).

Clinical Features

It accounts for 5–10% of penile carcinomas commonly arising in the glans, rarely in the foreskin. BC has a high incidence of nodal metastasis, with more than 50% of cases showing regional metastasis at presentation (Guimarães et al. 2009). The mortality rate due to systemic spread is very high (>60%), and particularly tumors deeply infiltrating the corpora cavernosa with a >10 mm diameter carry a bad prognosis.


BC presents as a large, ulcerated mass with endophytic, vertical growth deeply penetrating the corpora spongiosa (Fig. 1) and, frequently, the corpora cavernosa. Small foci of yellowish necrosis within the tumor may be present.
Fig. 1

Basaloid carcinoma. Cut section showing a deeply invasive nodular ulcerated mass infiltrating the corpora spongiosa and tunica albuginea


It is generally composed of a monotonous population of small to medium-sized cells with basophilic cytoplasm. The most frequent pattern is vertical growth (nodular), but some cases with a superficial spreading pattern have been reported. The nests are composed of anaplastic and small cells with round to oval nuclei, and mitoses are frequently observed (Fig. 2); other, more unusual, microscopic features are spindle cell features, a “starry sky” appearance due to individual cell necrosis and interstitial hyalinization. In the majority of BC cases, carcinoma in situ (CIS) is present adjacent to invasive carcinoma (Fig. 3). A common finding is lymphovascular and perineural invasion. The presence of squamous cell differentiation in less than 20% of the tumor is reported. A diffuse and trabecular small cell pattern may simulate neuroendocrine carcinoma. The presence of papillae with central fibrovascular core is feature of papillary-basaloid carcinoma (Cubilla et al. 2012).
Fig. 2

Basaloid carcinoma. Solid nests consisting of basophilic small ovoid basaloid cells with small nucleoli and mitoses

Fig. 3

Basaloid carcinoma. Neoplasm with prevalent basaloid component with vertical growth pattern and in situ component

Immunohistochemistry and Molecular Typing

BC is usually HPV-related and immunoreactive to p16, that is a surrogate for HPV detection (Chaux et al. 2014). HPV 16 is the most common genotype detected by PCR (Cubilla et al. 2010).

Differential Diagnosis

High-Grade Usual-Type Squamous Cell Carcinoma (SCC)

Usual-type SCC shows pleomorphic cells with abundant keratinized cytoplasm, while BC shows uniform nests of small cells throughout the tumor and keratinization is confined to the central area.

Urothelial Urethral Carcinoma (UUC)

UCC most frequently occurs adjacent to CIS and papillary urothelial carcinoma in the urothelial mucosa, and absence of p16 immunostaining and positivity for GATA3 support the urothelial origin.

Small Cell Neuroendocrine Carcinoma

Neuroendocrine carcinoma, in particular metastasis of Merkel cell carcinoma, has organoid, ribbon/trabecular features that are absent in BC. Immunohistochemical staining for CK 20 and neuroendocrine markers is sometimes necessary for a definitive diagnosis.

References and Further Reading

  1. Chaux, A., Cubilla, A. L., Haffner, M. C., Lecksell, K. L., Sharma, R., Burnett, A. L., & Netto, G. J. (2014). Combining routine morphology, p16 (INK4a) immunohistochemistry, and in situ hybridization for the detection of human papillomavirus infection in penile carcinomas: A tissue microarray study using classifier performance analyses. Urologic Oncology, 32(2), 171–177.CrossRefGoogle Scholar
  2. Cubilla, A. L., Reuter, V. E., Gregoire, L., Ayala, G., Ocampos, S., Lancaster, W. D., & Fair, W. (1998). Basaloid squamous cell carcinoma: A distinctive human papilloma virus-related penile neoplasm: A report of 20 cases. The American Journal of Surgical Pathology, 22(6), 755–761.CrossRefGoogle Scholar
  3. Cubilla, A. L., Lloveras, B., Alejo, M., Clavero, O., Chaux, A., Kasamatsu, E., Velazquez, E. F., Lezcano, C., Monfulleda, N., Tous, S., Alemany, L., Klaustermeier, J., Muñoz, N., Quint, W., de Sanjose, S., & Bosch, F. X. (2010). The basaloid cell is the best tissue marker for human papillomavirus in invasive penile squamous cell carcinoma: A study of 202 cases from Paraguay. The American Journal of Surgical Pathology, 34(1), 104–114.CrossRefGoogle Scholar
  4. Cubilla, A. L., Lloveras, B., Alemany, L., Alejo, M., Vidal, A., Kasamatsu, E., Clavero, O., Alvarado-Cabrero, I., Lynch, C., Velasco-Alonso, J., Ferrera, A., Chaux, A., Klaustermeier, J., Quint, W., de Sanjosé, S., Muñoz, N., & Bosch, F. X. (2012). Basaloid squamous cell carcinoma of the penis with papillary features: A clinicopathologic study of 12 cases. The American Journal of Surgical Pathology, 36(6), 869–875.CrossRefGoogle Scholar
  5. Guimarães, G. C., Cunha, I. W., Soares, F. A., Lopes, A., Torres, J., Chaux, A., Velazquez, E. F., Ayala, G., & Cubilla, A. L. (2009). Penile squamous cell carcinoma clinicopathological features, nodal metastasis and outcome in 333 cases. Journal of Urology, 182(2), 528–534.CrossRefGoogle Scholar

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Authors and Affiliations

  1. 1.Uropathology Unit, Department of PathologyFondazione IRCCS Istituto Nazionale dei Tumori di MilanoMilanItaly
  2. 2.Department of PathologyFondazione IRCCS Istituto Nazionale dei Tumori di MilanoMilanItaly