Sialadenoma papilliferum of a minor salivary gland with transformation to mucoepidermoid carcinomaN Sood1, B Arya1, R Gupta2, S Gupta2
1 Department of Pathology, Deen Dayal Upadhayay Hospital, Hari Nagar, New Delhi, India
2 Division of Cytopathology, ICMR-National Institute of Cancer Prevention and Research, I-7, Noida, Uttar Pradesh, India
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/jpgm.jpgm_912_21
Source of Support: None, Conflict of Interest: None
Keywords: Histopathology, malignant, mucoepidermoid carcinoma, sialadenoma papilliferum
Sialadenoma papilliferum (SP) is a rare salivary gland lesion categorized under ductal papillomas in the WHO classification of salivary gland tumors. The lesion is characterized by a biphasic pattern of exophytic and endophytic components, morphologically resembling the cutaneous eccrine tumor, syringocystadenoma papilliferum. Majority of the reported cases had a benign clinical course though occasional cases documented recurrence., The existence of malignant counterpart of SP has been debatable.
Two cases of malignant change in the endophytic component (one of epithelial-myoepithelial carcinoma and another mucoepidermoid carcinoma) have been reported to date., In addition, few authors have also reported dysplastic features in the exophytic component of SP.,, Such reports underscore a definite possibility of existence of a malignant counterpart of SP, which requires further research.
The present report describes the features of a case of sialadenoma papilliferum with mucoepidermoid carcinoma arising from a minor salivary gland as the third confirmed case of malignant transformation of this entity.
A 44-year-old man presented with an eight-month history of soreness in the right floor of mouth. Oral examination revealed an exophytic ulceroproliferative growth with papillary projections in the floor of mouth. Biopsy from the growth was reported elsewhere as a well differentiated squamous cell carcinoma. The patient underwent a right hemimandibulectomy with cervical lymph node dissection. We received the right mandibular specimen with six teeth in situ. A growth measuring 2 × 1 cm was seen in the floor of mouth almost reaching up to the superior resection margin but away from the other margins of resection.
Histopathology from the growth showed a dilated Bartholin's duct of sublingual gland with both exophytic and endophytic components. The exophytic part (intraductal) of the tumor was composed of papillary projections with fibrovascular cores lined by double layered lining epithelium of luminal columnar cells and basal cuboidal cells with scattered goblet cells [Figure 1]a, [Figure 1]b. Focal squamous metaplasia was noted without significant nuclear atypia. The fibrovascular cores showed lymphocytic infiltrate. The lesion was merging with an invasive component (endophytic) extending into the overlying buccal mucosa and sublingual gland. The endophytic lesion showed an invasive component composed of a solid pattern composed of predominantly intermediate cells along with atypical squamous cells and a few glandular structures [Figure 1]c, [Figure 1]d. The intermediate cells displayed vesicular nuclear chromatin, 1 to 2 nucleoli and scant to moderate amount of cytoplasm. Frequent mitotic figures were noted though no necrosis was seen. Perineurial invasion was noted. The goblet cell component and intermediate population was positive for CK7, MUC-1, and MUC-2 with a high Ki-67 labeling index and CK5 [Figure 2] was noted in the basal cells of SP and variable positivity in the rest of the tumor cells including intermediate cells and epidermoid cells. The adjoining salivary gland tissue showed lymphoplasmacytic infiltrate.
Based on the histopathological and immunohistochemical findings, the lesion was diagnosed as a mucoepidermoid carcinoma arising on a background of sialadenoma papilliferum. The resected margins and lymph nodes were free of tumor. The patient is currently being followed up.
SP was first described in 1969 by Abrams and Finck. The most common sites of occurrence include palate and buccal mucosa followed by upper lip, retromolar area, and parotid gland in occasional cases. SP affects males more than females and usually occurs after the 4th decade of life. The clinical appearance of SP may mimic squamous cell papilloma of the oral cavity, though no association has been found between SP and oral human papillomavirus infection. The histologic appearance of SP has been described extensively in the various reports.,, Majority of the reported cases of SP have been benign in nature and could be treated successfully by complete excision. However, rare cases of recurrence due to the lack of encapsulation around the glandular component are on record.,
An extensive literature review revealed only occasional case reports of SP with dysplastic features in the surface epithelium, suggesting a potential of malignant change.,, However, the cases reported by Ponniah, Anuradha et al., and Ide et al. did not feature any invasive component. Malignant transformation of SP is an extremely rare phenomenon. The first reported case of malignant SP by Solomon et al. with cervical lymph node metastasis has been refuted and considered as a primary mucoepidermoid carcinoma (MEC) by other authors. Shimoda et al. described the first well-documented case of SP with epithelial--myoepithelial carcinoma in the upper submucosa and high-grade carcinoma in deeper areas. The authors demonstrated areas of transition between the SP component and the malignant areas, ruling out the possibility of a collision tumor. Liu et al., in 2009, reported a SP with MEC where the superficial part of the lesion retained the configuration of SP. Hence, the present case appears to be, to the best of our knowledge, the third documented case of malignant transformation of SP. Similar to Liu et al., the present case showed the classical histopathological features of SP in the intraductal portion of the tumor. The invasive component of the tumor was composed of intermediate cells, squamous cells and few mucin-secreting cells, confirmed by immunohistochemistry. There were mitotic figures and high Ki-67 index, indicative of malignancy. The continuity of the exophytic SP-like features and endophytic MEC along with foci of squamous metaplasia confirms the malignant transformation of SP. In the present case, the initial biopsy consisted of the intraoral part showing malignant features. The component of SP was elicited on careful dissection of the minor salivary gland duct leading to the final diagnosis of SP with malignant transformation.
The biphasic appearance of SP is distinctive among salivary gland tumors. However, the papillary architecture of exophytic portion of the tumor may simulate a papillary cystadenocarcinoma, adenosquamous carcinoma with papillary features and papillary squamous cell carcinoma (SCC). Papillary SCC can resemble SP superficially; however, the endophytic glandular component is absent in SCC. Papillary cystadenocarcinoma does not feature squamous elements, unlike the present case. Adenosquamous carcinoma is composed of distinct glandular and squamous components within the tumor but no papillary configuration. The appropriate therapy for majority of SP that are benign is complete excision. Due to the extreme rarity of malignant SP, its clinical course and appropriate therapy is yet not defined.
In conclusion, the present report describes the third case of malignant sialadenoma papilliferum with mucoepidermoid carcinoma. Pathologists need to be aware of the possibility of malignant change in this rare lesion. Our case also highlights the importance of careful examination of the intratumoral ducts in such cases to unearth the intraductal component of the tumor. Documentation of more such cases of malignant SP in literature would assist in delineation of the biologic behaviour and better management of this entity.
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[Figure 1], [Figure 2]