Adenoid cystic carcinoma (ACC), also termed basal cell carcinoma (BCC) of the prostate, represents an extremely rare nonacinar prostatic malignancy [1]. These terms are used interchangeably in the literature to describe the same tumor entity, which is characterized by basal cell differentiation and architectural patterns analogous to salivary gland ACC. First described in the salivary glands by Billroth in 1859, ACC is histologically defined by cribriform, glandular, and basaloid growth patterns. Prostatic ACC/BCC is exceptional, with only limited case reports and small case series available in the literature [2]. Although earlier reports suggested an indolent clinical course, accumulating evidence indicates heterogeneous behavior, with approximately 25% of patients developing local recurrence or distant metastasis [1, 3, 4]. Owing to its rarity, standardized treatment protocols are lacking, and therapeutic strategies have included surgery, radiotherapy, chemotherapy, or combinations thereof, often with variable and unpredictable outcomes [5].
Here, we report a case of prostatic adenoid cystic (basal cell) carcinoma in a 69-year-old man presenting with hematuria, treated with radical prostatectomy and remaining clinically stable at six months of follow-up.

A 69-year-old man presented to the urology outpatient department with complaints of hematuria. Contrast-enhanced computed tomography (CECT) urogram revealed grade III prostatomegaly without evidence of a bladder mass. Serum PSA levels were within normal limits. The patient underwent transurethral resection of the prostate, and the resected chips were submitted for histopathological examination.
Grossly, approximately 8 g of prostatic tissue was received, aggregating to 5.5 × 3.5 × 1.5 cm. Microscopic examination revealed a malignant neoplasm composed of basaloid cells arranged in solid and cribriform patterns, with peripheral palisading. The tumor cells exhibited moderate nuclear pleomorphism and frequent mitotic figures. Foci of necrosis and perineural invasion were identified (Figure 1A, 1B). Figure 1A illustrates solid basaloid tumor nests with central comedo-type necrosis, while Figure 1B highlights marked cytological atypia with frequent mitotic figures at higher magnification.
On immunohistochemistry, tumor cells showed diffuse and strong positivity for HMWCK (Figure 2A), confirming basal cell differentiation, and BCL2 (Figure 2B), supporting a diagnosis of basal cell carcinoma of the prostate. Staining was negative for PSA, AMACR, GATA3, CK7, synaptophysin, CD56, and chromogranin, thereby excluding prostatic adenocarcinoma, urothelial carcinoma, and neuroendocrine neoplasms. The Ki-67 proliferative index was markedly elevated (60-65%) (Figure 2C), indicating a high proliferative activity and supporting a diagnosis of adenoid cystic (basal cell) carcinoma of the prostate. The patient subsequently underwent radical prostatectomy and remained clinically stable without evidence of distant metastasis at six months of follow-up.

Prostate cancer is the most prevalent malignancy among men and the second most common cancer worldwide [6, 7]. While the majority of cases are conventional acinar adenocarcinomas, approximately 5–10% represent nonacinar variants [8]. Among these, adenoid cystic (basal cell) carcinoma is exceptionally rare, with fewer than 150 cases reported to date.
Shibuya et al. reported a mean patient age of 65.3 ± 13.6 years [9], which is consistent with the age of our patient (69 years). One of the most important differential diagnoses of prostatic BCC is basal cell hyperplasia. Histopathological evaluation is pivotal in this distinction, as carcinoma demonstrates infiltrative growth, architectural complexity, cytological atypia, increased mitotic activity, necrosis, a desmoplastic stromal response, and a high Ki-67 proliferative index.
Basal cell carcinoma of the prostate exhibits considerable morphological heterogeneity. It may resemble salivary gland ACC with a cribriform architecture or present as a basaloid carcinoma analogous to cutaneous basal cell carcinoma [10, 11]. Some tumors show a single predominant histologic pattern, whereas others demonstrate a combination of basaloid and adenoid cystic components. Solid and basaloid growth patterns have been associated with more aggressive biological behavior [1, 9]. In a clinicopathological evaluation of 29 cases, Ali et al. described small solid nests with peripheral palisading and identified the adenoid cystic pattern as the predominant architecture [12], findings also supported by Shibuya et al. [9]. McKenney et al. reported extensive intraglandular hyalinization and infiltrative growth with extraprostatic extension and perineural invasion in basaloid carcinomas [13]. In the present case, both solid growth with necrosis and basaloid architecture were observed, suggesting a potentially aggressive phenotype.
Unlike conventional prostatic adenocarcinoma, ACC/BCC of the prostate typically presents with normal PSA levels. This observation in our patient is consistent with multiple published reports [9, 14-18]. Although previously regarded as an indolent tumor, recent studies have demonstrated variable clinical behavior. Shibuya et al. reported disease progression, including recurrence and metastasis, in 37% of patients [9], underscoring the malignant potential of this entity.
Treatment strategies for basal cell carcinoma of the prostate have included surgery, radiotherapy, chemotherapy, and hormonal therapy. Owing to the rarity of this entity, management recommendations are largely extrapolated from small case series and retrospective reviews. In a comprehensive review and discussion by Currò et al. [5], radical surgical excision was favored for organ-confined disease, as it provides optimal local control and allows accurate pathological staging. Radiotherapy has been proposed as an alternative in non-surgical candidates or in cases with locally advanced disease; however, long-term outcome data remain limited. Chemotherapy and androgen deprivation therapy have shown inconsistent responses and are generally reserved for metastatic or refractory disease.
In the present case, radical prostatectomy was selected due to localized disease, absence of distant metastasis, normal PSA levels, and the presence of high-risk histological features, including a solid basaloid growth pattern, necrosis, perineural invasion, and a markedly elevated Ki-67 proliferative index. These features have been associated with aggressive behavior and an increased risk of recurrence in published series. The patient was placed on close postoperative surveillance, consistent with recommendations by Currò et al., given reports of delayed local recurrence and distant metastasis even after apparently complete resection. Surveillance includes periodic clinical assessment and radiological imaging rather than PSA-based monitoring, as PSA levels are typically uninformative in basal cell carcinoma of the prostate [9, 18].
Systemic chemotherapy has been the most frequently employed treatment modality, with highly variable outcomes. Several cases demonstrated disease progression despite docetaxel-based or platinum-based regimens, even after only two treatment cycles. In contrast, occasional responses have been reported, including significant regression of pulmonary metastases with etoposide after failure of docetaxel-based therapy and prolonged survival following docetaxel treatment in select patients [19]. Table 1 depicts the brief literature review of the case reports published in the recent literature.

Adenoid cystic (basal cell) carcinoma of the prostate is an exceptionally rare malignancy with overlapping histopathological features that may delay diagnosis. This case underscores the critical role of immunohistochemistry in distinguishing ACC/BCC from more common prostatic neoplasms and highlights the need for heightened clinical awareness. Early recognition and multidisciplinary management are essential to optimize outcomes in this diagnostically challenging tumor.

Acknowledgements

None.

Ethical policy

The study was done in accordance with the Declaration of Helsinki. Informed patient consent was taken.

Availability of data and materials

That data is available from the corresponding author on request.

Author contributions

Shabana Andleeb Ansari: conceptualisation, data curation, formal analysis, writing original draft; Mohd. Mubashir Ali Khan: conceptualisation, formal analysis, review and writing; Azmat Kamal Ansari: conceptualisation, resources, data curation, supervision, review and editing; Beant Kaur: conceptualisation, formal analysis, review, writing and editing; Nagma Parveen: conceptualisation, formal analysis, review, writing and editing.

Competing interests

The authors declare that they have no competing interests.

Funding

None.

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