Malignant gastrointestinal melanomas of unknown origin: Should it be considered primary?

Rare Lacrimal Gland Melanoma: A Case Report and Treatment Insights

BACKGROUND Melanoma is a malignant transformation of melanocytes known for its capacity to metastasize, necessitating early diagnosis and intervention. While over 97% of melanomas are diagnosed with a known primary site, such as the skin, eye, or mucous membranes, rare cases like melanoma of unknown primary (MUP) can present with atypical manifestations, highlighting the need for comprehensive examinations. CASE REPORT In January 2023, a 68-year-old woman presented with a 4-week history of swelling and discoloration in her left upper eyelid, revealing a hard, livid mass indicative of malignancy. Surgery and subsequent histopathology confirmed epithelioid cell melanoma in the lacrimal gland. Although no other primary melanoma sites were found, imaging and biopsy in August 2023 identified metastatic spread to her lungs. Despite proton radiotherapy, progression led to thoracoscopic surgery for metastasis resection in September 2023. Further re-evaluation revealed metastases in both lungs, leading to her enrolment in a trial comparing PD-1 (programmed death ligand 1) antibody plus LAG-3 (lymphocyte activation gene 3) antibody with PD-1 monotherapy. Subsequent progression required treatment with ipilimumab and nivolumab, which resulted in near complete regression of the orbital tumor. Unfortunately, she later developed serious complications, including hypophysitis, lung infection, renal failure, and viral meningitis, which ultimately led to her death in April 2024. CONCLUSIONS This case report highlights the diagnostic challenge in distinguishing between melanoma of known and unknown primary origins. It emphasizes the importance of thorough histological work-up and heightened suspicion for melanoma of the lacrimal gland, despite its rarity, to ensure prompt diagnosis and treatment due to its metastatic potential.

Undetected metastatic melanoma in the colon

Colonic melanoma is a rarely detected aetiology of small bowel obstruction. This is a case of a male in his 80s with a history of treated stage IIIA melanoma on his trunk 7 years prior who presented with small bowel obstruction. He underwent urgent surgical intervention, where a partial colectomy was performed. Pathology revealed a 4.6 cm melanoma causing intussusception. This case highlights the insidious nature of metastatic melanomas and discusses an uncommon location of melanoma metastasis that evaded detection until a late stage.

Report on a case of liver-originating malignant melanoma of unknown primary

Malignant melanoma (MM) frequently occurs in the skin or mucosa, whereas malignant melanoma of unknown primary (MUP) is diagnosed in patients with lymph nodes or visceral organs as the site of origin, where it is challenging to detect the primary lesion by comprehensive examination. MUP is possibly related to the spontaneous regression of the primary lesion. In addition, primary hepatic melanoma (PHM) usually refers to the primary MM occurring in the liver, with no typical primary lesions and no manifestations of tumor metastasis. A 61-year-old male patient with liver as the site of origin was diagnosed with MM by Melan-A, HMB-45, and S-100 immunohistochemistry staining of liver biopsy tissue. Based on a comprehensive examination, no basis was found for melanoma in sites such as the skin, mucosa, five sense organs, brain, digestive tract, respiratory tract, or genitalia, and the patient was subsequently diagnosed with MUP. MMs require a comprehensive inspection, beginning with the liver, to search for the primary lesion; if the primary lesion is not found, the possibility of PHM or MUP should be considered.

Hypothesised cutaneous sites of origin of stage III melanomas with unknown primary: A multicentre study

Based on molecular evidence that melanomas with unknown primary (MUPs) arise from the skin, we hypothesised that sites of MUPs are disproportionately on trunk and lower limbs, sites that are not readily visible to patients and clinicians. We tested this hypothesis by inferring the anatomic site of origin of MUPs from the corresponding known cutaneous sites of melanoma patients with known primary tumours (MKPs). We analysed data from three separate cohorts of patients from Brisbane, Australia (n = 236); Manchester, UK (n = 51) and Padova, Italy (n = 33), respectively, who first presented with stage III melanoma with lymph node metastases. We matched two MKP patients to each MUP patient based on lymph node dissection (LND) site, age and sex, and imputed cutaneous sites of origin of MUPs from their two matched MKPs for study countries, giving two possible sites for each MUP per centre. Overall, results showed that MUP patients were predominantly male, and trunk was the most likely origin, comprising around a third to a half of MUPs across the three cohorts. The remaining MUP inferred sites varied by country. In the Australian cohort, the legs accounted for a third of imputed sites of MUPs, while in the UK and Italian cohorts, the most frequent site was the arms followed by the legs. Our findings suggest the need for regular and thorough skin examination on trunk and limbs, especially in males, to improve early detection of cutaneous melanoma and reduce the risk of metastatic disease at the time of presentation.

Management of Regional Lymph Nodes in Head and Neck Melanoma

The utilization of sentinel lymph node (SLN) biopsy has transformed the workup and staging of intermediate-thickness cutaneous melanomas. SLN biopsy, performed at the time of primary tumor excision, accurately maps lymph nodes at risk of harboring occult metastatic deposits from head and neck cutaneous melanomas and represents the current standard of care. Completion lymphadenectomy identifies additional tumor in 12% to 24% of SLN biopsy positive cases but does not affect melanoma-specific survival.

Primary Gastric Malignant Melanoma in a 68-Year-Old Woman: A Case Report and Review of the Literature

Non-cutaneous melanoma is a very rare clinical entity. Gastric melanoma can be primary or secondary, but determining their nature is in most cases very challenging. To date, very few cases of primary gastric melanoma have been described in the literature. We report the first case of primary gastric melanoma documented in a Romanian patient, confirmed through clinical, imagistic, and pathological diagnosis. A 68-year-old female patient presented to our hospital with complaints of dyspepsia, abdominal pain, and weight loss. Esophagogastroduodenoscopy revealed two large sessile masses in the gastric fundus, which was histologically compatible with melanoma; immunohistochemistry staining was positive for vimentin, S100 protein, HMB45 antibody and Melan A/MART1, and negative for pan-CKAE1/AE3, leukocyte common antigen and DOG1. Extensive dermatological and ophthalmological examinations did not identify a primary lesion. The patient was therefore diagnosed with primary melanoma of the stomach. At the time of the diagnosis, multiple bone and pulmonary metastases were detected and considering the poor general status of the patient, surgery was not recommended. She died three months following diagnosis. A review of the literature identified only 32 other reported cases of primary gastric melanoma, all in individuals ≥50 years of age and most of them in male patients. Partial or total gastrectomy was the usual treatment of choice, but prognosis was overall poor. Awareness of this rare condition must be increased among healthcare providers, as early detection can improve survival chances.

Primary Duodenal Melanoma: Challenges in Diagnosis and Management of a Rare Entity

Primary melanoma of the duodenum is an extremely rare, aggressive and life-threatening malignant neoplasm. Published data regarding the effectiveness of current treatment strategies is limited, and our knowledge relies mostly on sporadic case reports. The diagnosis of primary duodenal melanoma is challenging and is based on the patient's medical history and findings from physical examination and radiological and endoscopic imaging as well as proper and careful pathological examinations of the tumor. Despite the many advances in cancer treatment, the prognosis for patients with this type of melanoma remains extremely poor. Delayed diagnosis at advanced disease stage, the general aggressive behavior of this neoplasm, the technical difficulty in achieving complete surgical resection, along with the rich vascular and lymphatic drainage of the intestinal mucosa, all have a negative impact on patients' outcome. In the present review, we aimed to collect and summarize the currently available data in the literature regarding the pathogenesis, clinical features, diagnosis, management and long-term outcomes of this rare, malignant tumor, in order to expand knowledge of its biological behavior and investigate optimal therapeutic options for these patients. Additionally, we present our experience of a case involving a 73-year-old female with primary duodenal melanoma, who was successfully treated with complete surgical resection.

Current concepts of ectopic nodal inclusions with special emphasis on nodal nevi

Nodal inclusions of ectopic tissue within lymph nodes are seen comparatively often in dermatopathology and general pathology. Glandular and nonglandular epithelium, as well as melanocytic nevi can be observed within lymph nodes and represent mostly incidental findings without any relevance. The main challenge in reporting these morphologic features is to differentiate such benign inclusions from metastatic settlements of distinct organ tumors. As sentinel node biopsy and lymph node dissection have become standard procedure in clinical oncology and have an immense clinical impact, the correct evaluation of these nodal inclusions is indispensable to avoid undertreatment or overtreatment of patients. In addition, the genesis of these inclusions has not yet been satisfactorily clarified. Two concepts have been laid out: the theory of benign metastases and the migration arrest theory. However, neither theory has so far been able to answer the following questions: Why do we find more nodal nevi in patients with melanoma who had a sentinel node biopsy than in patients without melanoma, and why do we not find nodal nevi in deep visceral lymph nodes? We present a comprehensive review of the current knowledge on nodal inclusions, proposing a concept for the pathogenesis of nodal nevi, to answer these questions.

Primary Heptaic Melanoma or Melanoma of Unknown Primary?

Melanoma is the deadliest malignancy of the skin with an estimated 91 000 new annual cases with 9300 deaths in 2018. Metastatic disease generally presents with identification of known primary lesion; however, in 3.2% of patients, metastatic disease is discovered with unknown primary lesion/site. Rarely, melanoma is diagnosed as a primary lesion in visceral organs. Suspected primary hepatic melanoma is exceedingly rare and described in only a few case reports. We present the case of a 69-year-old Caucasian male who was found to have a hepatic melanoma on final pathology after resection of suspected primary hepatic malignancy. After a thorough postoperative workup, a primary lesion was unable to be identified. As such, a visceral primary lesion is considered.

Melanoma of unknown primary in the pancreas: should it be considered primary?

Background

Malignant melanoma is characterized as highly malignant due to its rapid growth and early metastasis. Metastatic melanoma from occult primary is rare. Melanoma of unknown primary in pancreas are even rear. But it is a biologically ill-defined and clinically understudied concept.

Case presentation

In this report, a 43-year-old man was diagnosed with pancreatic carcinoma. Extended total pancreatectomy together with portal vein reconstruction and extensive lymphadenectomy were performed in our hospital. The patient was diagnosed with pancreatic malignant melanoma after pathological examination. He was still alive 20 months after the operation without any evidence of recurrence.

Conclusion

The described case highlights the possibility of primary pancreatic malignant melanoma and the treatment strategies of this rare carcinoma.

Ileal Melanoma, A Rare Cause of Small Bowel Obstruction: Report of a Case, and Short Literature Review

BACKGROUND

Malignant melanoma frequently spreads to the gastrointestinal tract, with 60% of patients with advanced metastatic disease showing digestive involvement; however, primary MM of the small intestine is a controversial diagnosis. In fact, whether these lesions arise as true small bowel primary neoplasms or represent metastases from unidentified cutaneous melanomas remains debatable. The most common complications are intestinal obstruction, massive gastrointestinal bleeding, and perforation.

OBJECTIVE & METHODS

We report a case of a 64-year-old patient, with an unremarkable medical history, in which a late diagnosis of primary ileal malignant melanoma in the setting of an emergency laparotomy due to small bowel obstruction, and where PET-scan showed costal metastasis. Therefore, we provide a narrative review of the scientific literature about this topic.

RESULTS

36 cases of primary small bowel melanoma, included that in the present study, were found through our search in the scientific literature.

CONCLUSION

Primary small bowel MM appears to be an extremely rare entity which clinicians should be more aware of, in order to plan better a correct strategy of early diagnosis and appropriate treatment.

A Rare Case of Primary Gastric Melanoma

Primary melanomas in the gastrointestinal tract are extremely rare, with an estimated prevalence of 0.5 to 1 case per million. Primary mucosal melanomas of gastric origin account for approximately 1–3% of all primary melanomas in the gastrointestinal tract. We present the case of a patient who underwent surgery due to primary gastric melanoma.

Melanoma of unknown primary

Formally described in the 1960s, melanoma of unknown primary (MUP) is characterized by the finding of metastatic melanoma within the lymph nodes, subcutaneous tissues, and other distant sites without an evident primary lesion. The most likely hypothesis of its etiology is an immune-mediated regression of the primary after metastasis has occurred. In addition, patients with MUP appear to have equivalent or better outcomes compared with patients with known primaries of a similar stage.

Malignant Melanoma Metastasizes to Colonic Polyp

Malignant tumors metastasizing to the colon has been observed rarely. Gastrointestinal metastasis can present as benign, unpigmented polyps endoscopically. Most patients do not display any symptoms, and if symptomatic, they usually present with gastrointestinal bleeding. For patients with the history of melanoma, histopathology of polyp can change or alter the course of management. This is a case of a 74-year-old male diagnosed with recurrent melanoma of left ear. Colon cancer screening found blood in his stool. Colonoscopy displayed to have three polyps, one polyp was found to be malignant melanoma. The patient was started on Pembrolizumab, and was tolerating immunotherapy well with no new complaints three months later.

Metastatic Gallbladder Melanoma Presenting as Acute Emphysematous Cholecystitis

Malignant melanoma is an aggressive tumor with a high potential for distant metastases, including spread to the gallbladder where it represents more than half of all metastases detected at autopsy. Yet, it is rarely symptomatic in life and is a rare cause of acute cholecystitis. Emphysematous cholecystitis is a rare, potentially fatal variant of acute cholecystitis characterized by the presence of gas in the gallbladder lumen or wall. We report a 77-year-old woman with acute emphysematous cholecystitis as the initial feature of recurrent melanoma metastatic to the gallbladder. This exceptional association highlights the need to consider a relapse of malignancy when assessing unexplained abdominal symptoms in any patient with a prior history of melanoma.

Primary malignant melanoma of the small intestine: a report of 2 cases and a review of the literature

The majority of malignant melanomas in the small intestine are metastases from primary cutaneous lesions, it can also develop as a primary mucosal tumor in the gastrointestinal tract. In this report, we present rare cases of primary small bowel melanoma and review the current literature. A 78-year-old male presented with abdominal pain and CT enterography identified a ileal mass. A 79-year-old female presented with signs and symptoms of partial small bowel obstruction. Abdominopelvic CT and small bowel series revealed a obstructing mass in the distal jejunum. The masses were confirmed on laparotomy and histologically diagnosed as melanoma. Extensive postoperative clinical examination revealed no cutaneous lesions. A primary small bowel melanoma is an extremely rare neoplasm. A definite diagnosis can only be made after a thorough investigation has been made to exclude the coexistence of a primary lesion. Curative resection of the tumor remains the treatment of choice.

Stage IV melanoma of unknown primary: A population-based study in the United States from 1973 to 2014

BACKGROUND

Melanoma of unknown primary (MUP) is incompletely described on a population level.

OBJECTIVE

We sought to characterize stage IV MUP in a population-based cancer registry.

METHODS

We developed a novel search algorithm to identify cases of stage IV MUP in the Surveillance, Epidemiology, and End Results 18 registries from 1973 to 2014. Cases of stage IV melanoma of known primary (MKP) served as a comparison group. Age-standardized incidence rates, demographic characteristics, adjusted disease-specific survival, and Cox proportional hazard models were calculated for MUP and MKP.

RESULTS

A total of 322 stage IV MUP cases and 12,796 stage IV MKP cases were identified in Surveillance, Epidemiology, and End Results 18 registries from 1973 to 2014. The incidence of stage IV MUP is increasing, particularly for patients younger than 30 years of age. In multivariate analyses, age older than 50 and a lack of surgical treatment were negative prognostic factors for stage IV MUP. Relative survival, but not 5-year adjusted disease-specific survival, was higher for stage IV MUP than for MKP.

LIMITATIONS

Limitations include the retrospective study design and possible misclassification of MUP.

CONCLUSIONS

The incidence of stage IV MUP is increasing, and stage IV MUP shares similar prognostic factors with stage IV MKP, including age and surgical treatment.

Primary melanoma of the small bowel revealed by gastrointestinal bleeding: a case report

Background

Primary melanoma of the small bowel is extremely rare. Only a limited number of cases have been described in the literature. Mostly, the small intestine is affected by metastatic tumors of other primary lesions, especially cutaneous.

Case presentation

We report the case of a 75-year-old North African woman with a small bowel melanoma. The diagnosis was made by histological examination and immunohistochemical profile matching after a segmental small bowel resection. Postoperative investigations looking for cutaneous, gastrointestinal or ocular primary lesions found no abnormalities.

Conclusions

The diagnosis of primary small bowel melanoma can be retained although it remains difficult to exclude the possibility of metastatic melanoma.

Primary small bowel melanomas: fact or myth?

Small bowel melanoma (SBM) is a rare entity, which often evades diagnosis and therefore presents late. Its origin, whether arising primarily or metastatically from an unidentified or regressed primary cutaneous melanoma, remains debatable. In this report, we present a rare case of primary SBM and review the current literature. A 60-year-old man presented with melena and microcytic anemia. A series of investigations including abdominal ultrasonography (US), esophago-gastro-duodenoscopy (EGD) and colonoscopy were normal. Abdominal computed tomography revealed no specific pathology. Subsequent capsule endoscopy identified a jejunal mass, which was confirmed on laparotomy, was resected, and histologically diagnosed as melanoma. Extensive postoperative clinical examination revealed no cutaneous lesions. This report discusses gastrointestinal (GI) malignant melanoma, and examines the evidence both for and against the existence of true primary vs. metastatic disease. Furthermore, this case highlights the capabilities of capsule endoscopy in identifying an extremely rare GI tumor, which evaded other diagnostic modalities. Finally, the origins and pathophysiology of this rare cancer are evaluated, with the aim of promoting early diagnosis and treatment, and therefore improving current poor outcomes.

Primary small bowel melanoma. A case report and a review of the literature

Primary malignant melanoma originating from the small intestine is extremely rare. Only a limited number of cases are described in the literature. Most commonly small intestine is affected by metastatic tumors from other primary lesions. We present a case of a 68-years old male diagnosed with primary malignant melanoma as an ulcerated and bleeding mass in the jejunum--located 40 cm away from the Treitz band. In our case the diagnosis was confirmed at laparotomy and enterectomy. Histology revealed a neoplastic infiltration involving the entire intestinal mucosa, with atypia of neoplastic cells and immunoreactivity to HMB45(+), Melan A(+) and S100(+), confirming the diagnosis of melanoma. There was not revealed a primary lesion in the skin, eye, anus, rectum or in other location by the post-operative investigation. An eleven-month close follow-up has not revealed any metastasis. Therefore a definitive diagnosis of primary malignant melanoma was set.

Palliative radiation therapy for primary gastric melanoma

INTRODUCTION

Primary gastric melanoma is an exceedingly rare cause of upper gastrointestinal bleeding (GI bleeding). Prior reports of primary gastric melanoma have mostly been treated with surgery with utilization of radiation therapy being unreported. Radiation therapy has been used to palliate bleeding of other cancers including lung, bladder, cervix, and more recently primary gastric cancers.

CASE PRESENTATION

This case documents an 87-year-old male who presented with fatigue and melena, and was found to have severe anemia. Endoscopy with biopsy revealed an isolated focus of melanoma. After discharge, he presented two days later and was found to have continued bleeding. Because he was deemed a poor surgical candidate he elected to undergo palliative radiation therapy for bleeding control.

DISCUSSION

The diagnosis of primary verses metastatic melanoma is a topic of debate. Case reports of patients with no known extra-gastric primary have undergone surgical treatment with varying outcomes. Patients with metastatic gastric melanoma have relied on chemotherapy and radiation in addition to surgery, with radiation being used in the palliative setting. The use of radiation to control bleeding in other cancers including primary gastric adenocarcinoma has been previously studied. This case documents the utilization of radiation therapy in bleeding due to primary gastric melanoma.

CONCLUSIONS

Radiation therapy can provide adequate bleeding palliation in patients with primary gastric melanoma.

Survival after resection of a primary malignant melanoma of the small intestine in a young patient: report of a case

The occurrence of primary melanoma of the small intestine is rare. We describe the case of a 25-year-old man found to have a primary melanoma of the ileum. The patient presented with gradual onset of abdominal pain, fever, diarrhea, weight loss and fatigue. A preoperative diagnosis of a small intestinal tumor was based on the findings of computed tomography scanning. This diagnosis was confirmed at laparoto-my and a partial small bowel resection was performed. Histopathological examination of the resected specimen clarified the exact nature of the lesion, confirming the diagnosis of melanoma. Thorough postoperative investigation did not reveal a primary lesion in the skin, gastrointestinal tract, oculus or brain. Thus, we diagnosed this tumor as a primary lesion. One year after his operation, the patient remains well without any evidence of recurrence. Thus, we diagnosed this small bowel tumor as a primary melanoma of the small intestine.

Melanoma of stomach

INTRODUCTION

Melanoma of gastrointestinal tract can be either primary or secondary to metastases from other sites like skin, mucous membranes, and uvea. Primary gastrointestinal melanoma is rare and still rarer is stomach involvement.

CASE REPORT

We report a case of primary malignant melanoma of stomach in a 50-year-old female who presented with an axillary lymphadenopathy.

CONCLUSION

Melanoma of stomach is rare. It has characteristic endoscopic appearance. Differentiation of primary from secondary melanoma is possible on clinical behavior and histological characteristics.

Presumed melanoma-associated retinopathy (MAR): a presenting sign of primary small intestinal melanoma?

Melanoma-associated retinopathy is a paraneoplastic retinopathy associated mostly with cutaneous melanoma. In most cases it presents months to years after diagnosis of primary cutaneous melanoma was made or after recurrence. We describe a 55-year-old male patient who presented with symptoms of decreased vision and photopsia. Diagnosis of melanoma-associated retinopathy was made, but no primary cutaneous melanoma was found. 3 months later he developed intestinal perforation due to small intestinal melanoma.

Intussusception of the small intestine caused by a primary melanoma?

Although the gastrointestinal tract is a fairly frequent site of melanoma metastases, reports of small bowel intussusception caused by melanoma are very rare. We report the case of a 77-year-old man who was admitted to our hospital with epigastric pain, melena and anaemia. After clinical examination, laboratory evaluation and radiological work-up the diagnosis of a jejunal intussusception was made. Exploratory laparoscopy revealed a large tumour arising from the jejunum, approximately 20 cm distal to the angle of Treitz. Small bowel resection with an end-to-end anastomosis was performed. Histological examination showed an intestinal melanoma. There are different theories concerning the origin of malignant melanoma in the small bowel. Although the small and large intestines normally contain no melanocytes, these cells have occasionally been found in the alimentary and respiratory tracts and even in lymph nodes, which supports the theory of a primary origin of melanoma at these sites. Since this was a solitary intestinal lesion and there was no history of cutaneous melanoma, we conclude that this could be an example of a very rare primary melanoma of the small intestine.

Malignant gastrointestinal melanoma with an unknown primary

Malignant melanoma is rare in India; melanoma presenting as a metastatic disease with an unknown primary, involving the gastrointestinal tract without involving lymph nodes is extremely uncommon. We report a case of a 28-year-old male with a malignant melanoma metastasizing to stomach and liver with an unknown primary. Relevant literature is being reviewed.

Symptomatic malignant melanoma presenting as multiple gastrointestinal polyps

We report on a 66-year-old man with a past medical history of gout who presented to his general practitioner (GP) in July 2009 with a history of nausea and intermittent diarrhoea. He had lost 6 kg in weight over 6 months. His GP found he was anaemic and referred him to a gastrointestinal outpatient clinic. He went on to have a gastroscopy and colonoscopy, which revealed multiple polyps in the stomach, duodenum and colon. Histology revealed that all the polyps were malignant melanoma. He had no known history of malignant melanoma. A staging CT scan revealed multiple lung metastases and he was referred for palliative care. The patient died 4 months after diagnosis.

Epithelioid melanoma of the rectum: reappraisal of a deceptive microscopic simulator

We report 2 cases of rectal melanoma. The patients were a 48-year-old man and an 88-year-old woman. In both cases, the tumor presented as polypoid and necrotic masses, making initial diagnostic assessment difficult because of the regressive tissue changes. Microscopically, tumors were mostly composed of epithelioid, highly atypical cells mimicking poorly differentiated carcinoma or large cell lymphoma. Tumor cells were negative for keratin, leukocyte common antigen, and epithelial membrane antigen and positive for S100 protein and several melanoma markers, although in endoscopic biopsy specimens, the positive reaction was focal due to the limited viable tissue. One patient was treated with abdominoperineal resection. Pathologic examination of the surgical specimen revealed a polypoid mass infiltrating the muscle coat of the rectum. Local lymph nodes contained metastatic deposits. Microscopic examination of the rectal mucosa adjacent to the infiltrating neoplasm revealed colonization of the intestinal crypts by atypical melanocytes. This patient is alive 1 year after surgery with no evidence of recurrent disease. The other case was not deemed amenable to radical surgery because of the patient's advanced age and evidence of diffuse metastatic disease. She was alive 6 months after the initial diagnosis but was lost to follow-up. Data indicate that the diagnosis of melanoma, although feasible in large resection specimens, may be problematic in endoscopic biopsy, especially when only small tissue fragments are available and tumor regression hampers the accuracy of immunohistochemical stains. Documentation of intracryptic atypical melanocytes in nonneoplastic mucosa conceptually corroborates claims that rectal melanoma is related to preinvasive precursors as in cutaneous melanoma.

Melanoma of the small intestine

Intestinal melanomas can be primary tumours or metastases of cutaneous, ocular, or anal melanomas. Primary intestinal melanoma is extremely rare, whereas metastatic melanoma of the small bowel is common because of the tendency for cutaneous melanoma to metastasise to the gastrointestinal tract. Because distinguishing between primary and metastatic intestinal melanoma can be difficult, the main features of each are discussed, and the diagnostic images used to detect intestinal melanoma are assessed. Routine barium examinations and CT have limited sensitivity, but PET imaging can improve detection of melanoma metastases to the small bowel. Although various treatment strategies have been tried in patients with intestinal melanoma, surgical removal of intestinal metastases is the treatment of choice in patients with resectable tumours. No systemic therapy improves survival in patients with melanoma metastatic to the intestines; thus, the prognosis for these patients is poor. Patients with primary melanoma of the small intestine have a worse prognosis than do patients with metastases of cutaneous melanoma.