Primary Cutaneous Adenoid Cystic Carcinoma of the Back: A Case Report.

Adenoid cystic carcinoma (ACC) is a rare type of carcinoma that arises from the salivary glands. When ACC is present on the skin with no other primary site of malignancy in the body, it is termed primary cutaneous adenoid cystic carcinoma (PCACC). The only way to differentiate between ACC and other benign cutaneous masses is through the use of histopathology and immunohistochemistry. This case report describes a 67-year-old Asian female with a history of an epidermal inclusion cyst. She was seen in consultation with general surgery for the removal of a mass on her lower back. The initial excision's pathology revealed an ACC with perineural invasion. However, there were positive margins, as the mass was originally thought to be benign. Consequently, she underwent a second procedure for the total excision of the mass, resulting in subsequent negative margins. The patient was referred to radiation oncology; however, she ultimately opted to defer postoperative adjuvant radiation therapy, with the understanding that she would undergo biannual screening examinations.

A Multi-Modality Treatment of Retroperitoneal De-Differentiated Liposarcoma.

BACKGROUND Retroperitoneal sarcomas are rare tumors, only affecting 2 to 5 people per million population and accounting for 0.1% of all malignancies. Liposarcoma is the most common of all retroperitoneal sarcomas, responsible for approximately 20% of all sarcomas in adults. The most important prognostic factors are tumor grade, the presence of positive margins, tumor integrity, and degree of resection. CASE REPORT Our patient was a 73-year-old man with abdominal pain whose CT scan of the abdomen and pelvis demonstrated a 15×15 cm heterogeneous, left-sided intra-abdominal mass. He underwent resection of the retroperitoneal tumor, left colectomy, and left nephrectomy. Final pathology demonstrated a high-grade, de-differentiated liposarcoma with a rhabdosarcomatous component. The postoperative course was complicated by a small intra-abdominal abscess and abdominal dehiscence. a CT scan after surgery showed a residual tumor of the retroperitoneal posterior margin. Re-exploration to resect the residual tumor and repair the fascial dehiscence were performed. The patient underwent an initial chemotherapy regimen with doxorubicin, then moved to targeted therapy with Palbociclib, and is now on chemotherapy using Eribulin. CONCLUSIONS Achieving complete resection and the grade of the tumor at diagnosis are the 2 most important prognostic factors for patient survival in retroperitoneal liposarcoma, as survival rates are inversely proportional to the grade of the tumor. Even with the best resection attempts, there is always a risk of residual tumor cells within the tumor bed, which contribute to recurrence and need for additional surgical interventions. It is important to approach this disease process with a multidisciplinary team that includes surgical, medical, and radiation oncology to ensure the best survival outcomes. Retroperitoneal sarcoma recurrence and survival are directly related to the ability to achieve negative margins of resection, as well as the grade and size of the primary tumor. Adjuvant therapies that include radiation and immunotherapy may be effective in treating recurrent disease.

A Challenging Case of Retroperitoneal Abscess in a Post-Partum Crohn's Disease Patient.

BACKGROUND Crohn's disease (CD) is an inflammatory bowel disease affecting approximately 1 in 3000 people in the United States. Since the inflammation of CD is transmural, patients are at risk for fistula and abscess formation. Retroperitoneal abscesses are one type of which physicians must be aware. CASE REPORT We present the case of a 29-year-old woman with CD who complained of right hip and flank pain that began when she was 6-months pregnant. After delivery, she continued to complain of severe right flank pain and was admitted to the hospital 1 month later. CT scan imaging revealed a complicated retroperitoneal and right flank abscess, possibly due to a colonic intramural fistula. She developed severe acute necrotizing soft-tissue infection requiring 13 days of intensive care. She required debridement of the necrotizing infection of the right flank, drainage of the abscess, and washout for intraperitoneal sepsis. The patient tolerated the procedures well and was discharged 1 month later. CONCLUSIONS Given that the clinical manifestation of retroperitoneal fistula with abscess is insidious and its formation is less common than intraperitoneal abscesses, we hope healthcare providers learn from this case to avoid morbidity and mortality. When presented with a pregnant CD patient complaining of nonspecific abdominal symptoms, providers should consider fistulization and/or abscess formation. The option to evaluate pregnant patients using noninvasive methods, such as ultrasound or low-dose CT scan, can decrease radiation exposure to the fetus and prevent delays in diagnosis and treatment.

VARIABLE SELECTION IN NONPARAMETRIC ADDITIVE MODELS.

We consider a nonparametric additive model of a conditional mean function in which the number of variables and additive components may be larger than the sample size but the number of nonzero additive components is "small" relative to the sample size. The statistical problem is to determine which additive components are nonzero. The additive components are approximated by truncated series expansions with B-spline bases. With this approximation, the problem of component selection becomes that of selecting the groups of coefficients in the expansion. We apply the adaptive group Lasso to select nonzero components, using the group Lasso to obtain an initial estimator and reduce the dimension of the problem. We give conditions under which the group Lasso selects a model whose number of components is comparable with the underlying model, and the adaptive group Lasso selects the nonzero components correctly with probability approaching one as the sample size increases and achieves the optimal rate of convergence. The results of Monte Carlo experiments show that the adaptive group Lasso procedure works well with samples of moderate size. A data example is used to illustrate the application of the proposed method.