Laboratory data demonstrate abnormally elevated levels of serum gamma globulin and/or IgG, or the presence of autoantibodies. III. Histopathologic examination of the pancreas shows fibrotic changes with lymphocyte and plasma cell infiltrate.For diagnosis, criterion I (pancreatic imaging) must be present with criterion II (laboratory data) and/or III (histopathologic findings).Mayo Clinic has come up with five diagnostic criteria  called HISORt criteria which stands for histology, imaging, serology, other organ involvement, and response to steroid therapy. Radiologic features
Computed tomography (CT) findings in AIP include a diffusely enlarged hypodense pancreas or a focal mass that may be mistaken for a pancreatic malignancy. A low-density, capsule-like rim on CT (possibly corresponding to an inflammatory process involving peripancreatic tissues) is thought to be an additional characteristic feature (thus the mnemonic: sausage-shaped). Magnetic resonance imaging (MRI) reveals a diffusely decreased signal intensity and delayed enhancement on dynamic scanning. The characteristic ERCP finding is segmental or diffuse irregular narrowing of the main pancreatic duct, usually accompanied by an extrinsic-appearing stricture of the distal bile duct. Changes in the extrapancreatic bile duct similar to those of primary sclerosing cholangitis (PSC) have been reported.The role of endoscopic ultrasound (EUS) and EUS-guided fine-needle aspiration (EUS-FNA) in the diagnosis of AIP is not well described, and EUS findings have been described in only a small number of patients. In one study, EUS revealed a diffusely swollen and hypoechoic pancreas in 8 of the 14 (57%) patients, and a solitary, focal, irregular mass was observed in 6 (46%) patients.
: 676

Type III – obesity and pseudoacanthosis nigricans
In young persons, acanthosis nigricans is a visible marker which strongly suggests insulin resistance. Higher than normal insulin levels in the blood stream cause the growth of darkened skin over certain areas of the body. No skin treatment will get rid of AN. Acanthosis nigricans may lighten up and possibly go away by treating the root cause, insulin resistance, but it can take months or years to do so. Insulin resistance syndromes may be divided into type A (HAIR-AN) and type B syndromes. : 978 The majority of cases of acanthosis nigricans are associated with obesity and otherwise idiopathic. This is likely because of insulin resistance and more likely to occur in darker-skinned persons. : 968  This can also be referred to as pseudoacanthosis nigricans. : 86  In some cases, AN attributable to obesity and insulin resistance will occur on ones face. Most typically it will be present as a horizontal band on the forehead, but may also appear as perioral hyperpigmentation, periorbital hyperpigmentation, or generalized facial skin darkening. Type IV – drug-related
Acanthosis nigricans has been linked to the use of nicotinic acid, glucocorticoid use, combined oral contraceptive pills, and growth hormone therapy. : 86

Type V – malignancy
Malignant acanthosis nigricans: 86  refers to acanthosis nigricans occurring as a paraneoplastic syndrome associated with a cancer. Malignant acanthosis nigricans is most commonly associated with gastrointestinal adenocarcinomas, as well as genitourinary cancers such as those of the prostate, breast, and ovary. Other cancers, such as those of the lung, stomach, and lymphoma, are occasionally associated with acanthosis nigricans.