Adenoid cystic carcinoma (ACC) of the prostate gland which is also referred to as basaloid carcinoma and adenoid cystic-like tumour, was stipulated to have been first described in 1974 as a rare but distinctive variant of adenocarcinoma of the prostate gland. [1]. It has been pointed out that adenoid cystic carcinoma of the prostate gland (ACCP) is histologically identical to adenoid cystic carcinoma of the salivary glands [1] [2]. It has also been iterated that ACC is typically a salivary gland tumour which is composed of ductal and myoepithelial cells, but ACC could also arise in different sites, including the skin, cervix, and the breast.[3] [4] [5] [6] It has been iterated that for a long time, two reasons have been postulated for the independent existence of ACC: firstly, myoepithelial cells are not indigenous to the prostate gland, and secondly, adenoid cystic morphology occurs along a spectrum of basaloid proliferations which encompass basal cell hyperplasia, basal cell adenoma, and basal cell carcinoma. Finally, in 2016, World Health Organization (WHO)Classification of Tumours of the Urinary System and Male Genital Organs had categorized adenoid cystic hyperplasia carcinoma and basaloid variants as malignant basal cell tumours (BCC) [7]. It has been pointed out that ACCP/BCCP is an extremely rare variant of prostate cancer which is histologically difficult to detect, with uncertain biological behaviour [1]. Less than 160 cases of ACCP/BCCP had been reported in the literature compared to over 1 million acinar prostate cancer cases which are diagnosed every year. The age of onset cases of ACCP/BCCP has ranged from 28 years to 97 years, with peak incidence between 60 years and 75 years; nevertheless, cases of young adults had been reported [1]. It has been documented that when occurring in the prostate gland, ACCP/BCCP tumours do predominantly or most often show local infiltrative behaviour [1].

In view of the rarity of ACCP/BCCP, treatment options for the management of patients who are afflicted by ACC/BCC of the prostate are scarce. [1] it has been pointed out that majority of patients who are afflicted by ACCP/BCCP have tended to be treated with hormone therapy, radiotherapy, radical prostatectomy, or a combination of these treatments, even though generally the outcomes had remained poor [1]. Some of the earlier reports on ACCP/BCCP had reported these tumours as portending indolent biological behaviours; however, a number of recent reports had documented aggressive biological behaviour of the tumours as well as tumours associated with poor prognosis despite combination modality treatment. It has been pointed out that in cases of ACCP/BCCP, young age, involvement of the peripheral zone of the prostate gland by the tumour, extra-prostatic spread of the tumour, and perineural and peri-glandular invasion of the tumour are important prognostic factors. [1] It has been pointed out that the presence of these factors does make the undertaking of radical prostatectomy alone insufficient to guarantee control of the disease, therefore a combined treatment including adjuvant radiotherapy should be considered as a standard treatment of care. [1] There is no global consensus opinion regarding the best treatment options for ACCP/BCCP. It has been pointed out that no conclusive data could be drawn on the best systemic treatment, nor on the efficacy of androgen deprivation therapy, especially in view of the fact that ACCP/BCCP had proven to be independent from androgen stimulation [1]. [8] [9] It has been documented that recently, a phenotypic multi-dimensional assay testing the patient’s tumour tissue against different drug combinations had been promulgated, along with an accurate prediction of clinical outcome, thus offering a personalized way to select the most appropriate treatment option for the individual patient, especially with rare cancers.[10] [11] A more accurate refinement of the histopathology examination features of ACC/BCC of the prostate gland could probably be helpful with regard to the tailoring of treatment based upon tumour phenotypes and involved genetic pathways which includes various potential therapeutic targets [12]. It has been iterated that in view of the fact that prospective studies are not conceivable due to the rarity of ACCP/BCCP globally, the collection of real-world data, possibly with large international, retrospective databases would desirable in order to better understand the adequate management of ACCP/BCCP and the role of different therapeutic strategies [1]. Considering that majority of clinicians in the world have never encountered cases of ACCP/BCCP before, it would be envisaged that majority of clinicians would not be aware of the diagnostic features, treatment options and outcome following various treatment options of ACCP/BCCP. It would also be envisaged that many clinicians would not be aware of the difficulties that oncologist and urologist in the world face with regard to their dilemma in deciding on the most appropriate treatment options that would help provide treatment of curative treatment for localized ACCPs/BCCPs and well treatment options for locally advanced ACCPs/BCCPs. The ensuing article is divided into two parts (A) Overview of Adenomatoid Cystic Carcinoma /Basal Cell Carcinoma of the Prostate Gland and Miscellaneous Narrations from Case Reports, Case Series and Studies Related to Adenomatoid Cystic Carcinoma /Basal Cell Carcinoma of the Prostate Gland.

Aim

To review and update the literature on adenoid cystic (basal cell) carcinoma of the prostate gland.